paleoenvironmental changes in the western mediterranean since the last glacial maximum high resolution multiproxy record from the algero balearic basin abstract the present study uses a multiproxy approach in order to further understand the evolution of climate responses in the western mediterranean as of the last glacial maximum sediments from odp site 975 in the algero balearic basin have been analysed at high resolution both geochemically and mineralogicallly the resulting data have been used as proxies to establish a sedimentary regime primary marine productivity the preservation of the proxies and oxygen conditions fluctuations in detrital element concentrations were mainly the consequence of wet arid oscillations productivity has been established using ba excess according to which marine productivity appears to have been greatest during cold events heinrich 1 and younger dryas the s1 time interval was not as marked by increases in productivity as was the eastern mediterranean in contrast the s1 interval was first characterized by a decreasing trend and then by a fall in productivity after the 8 2 ky bp dry cold event since then productivity has remained low here we report that there was an important redox event in this basin probably a consequence of the major oceanographic circulation change occurring in the western mediterranean at 7 7 ky bp this circulation change led to reventilation as well as to diagenetic remobilization of redox sensitive elements and organic matter oxidation comparisons between our paleoceanographic reconstruction for this basin and those regarding other mediterranean basins support the hypothesis that across the mediterranean there were different types of responses to climate forcing mechanism the algero balearic basin is likely to be a key area for further understanding of the relationships between the north atlantic and the eastern mediterranean basins

anoxic vs dysoxic events reflected in sediment geochemistry during the cenomanian turonian boundary event cretaceous in the umbria marche basin of central italy abstract one of the most spectacular expressions of global oceanic anoxic events oaes of the cretaceous is the livello bonarelli of central italy deposited during the cenomanian turonian boundary event ctbe or oae2 at around 93 5 ma at furlo in the umbria marche basin in italy the bonarelli consists of approximately 1 m of c org rich shales interbedded with radiolarian rich layers and contrasts sharply with the extensive over and underlying siliceous limestones several minor c org rich intervals herein termed black levels average thickness 4 5 cm are interbedded within the scaglia bianca beneath the bonarelli x ray fluorescence and icp ms analyses show that these sediments consist of different mixing systems with three end members 1 sio 2 caco 3 scaglia bianca 2 average shale caco 3 black levels and 3 average shale sio 2 bonarelli given the sharp lithologic contacts and the little geochemical mixing between the groups these are thought to represent rapid switching events between sedimentary modes major element concentrations are generally low except for si and p owing to dilution by silica up to 96 and carbonates as al normalised ratios for elements such as ti or zr taken as proxies for higher energy environments are close to average shale values excess sio 2 is most likely linked to biogenic processes rather than quartz element al ratios of ti mg k rb and zr are fairly constant pointing to a mostly homogeneous source area the black levels and bonarelli are characterised by lower mg al ratios compared to the scaglia bianca sediments suggesting variability in chlorite input which could be linked with short term sea level drops indicated by ti al ratios the bonarelli sediments are severely depleted in mn which is indicative of oxygen depleted bottom water conditions and an open marine environment while the black levels appear to have been deposited in a much more restricted setting a model involving partial physical isolation of the furlo site by a sill coupled to omz variations by extra basinal forcing mechanisms is proposed to account for these conflicting data based on re mo ratios the bonarelli sediments were deposited under varying oxygen depletion levels from suboxic to anoxic while re mo ratios in the black levels show deposition under less oxygen deficient conditions most minor elements many of them redox sensitive or sulphide residing are strongly enriched in the c org rich sediments further documenting the absence of oxygen and potential availability of hydrogen sulphide in the water column at times while high zn concentrations suggest elevated submarine hydrothermal activity during this time interval ba is also present in very high concentrations up to 1 4 with an average weighed concentration of 0 6 for the entire bonarelli and is probably indicative of high paleoproductivity in this area this is further supported by high p concentrations hinting at nutrient availability at this site

stable isotope anomalies in mediterranean pleistocene records oxygen and carbon isotope records of twelve mediterranean cores raised from west alboran sea to east off israel and of four atlantic cores raised from the western side of gibraltar and located respectively inside below and beyond the modern mediterranean outflow are compared to open ocean records of core 71 139c from the north atlantic and core v19 30 from the east pacific oxygen isotope stratigraphies can be established for deep mediterranean records and the major events of the last 150 ka are easily identifiable for instance the five substages of stage 5 or the 18 ka event stage 2 are identified but the 10 ka event younger dryas is only recorded by globigerina bulloides and benthic foraminifera suggesting that the cooling affected only winter sst 14c dates for the two terminations ia and ib of the last deglaciation which are recorded in sediment cores from areas with high sedimentation rates faro ridge alboran sea sicilian strait are in good agreement with the dates published for the same termination in atlantic cores an intermediate step however has been identified in some cores at 14 ka and divides termination ia into two phases oxygen isotope anomalies are recorded by the shallow water species globigerinoides ruber they correspond to 1 a higher amplitude glacial interglacial change in 18o values which exceeds that of the open ocean by 1 in the western basin and by 1 7 in the eastern basin 2 large isotopic depletions during the deposition of sapropel s1 s3 and s5 they are interpreted as the result of fresh water run off responsible for a strong dilution in the shallower layers of the east mediterranean waters the isotopic effect of this dilution averages 0 75 for sapropel s1 and 1 6 for sapropel s5 during the last glacial maximum the mediterranean still acted as a concentration basin and a gradient of 18o values similar to the modern one 0 75 existed from west to east in the deep waters apparently deep water temperatures were lower during the last glacial but the decrease did not exceed 4 c in the eastern basin major anomalies are also contained in the 13c records of g bulloides and benthic foraminifera the 13c records from surface intermediate and deep waters of the eastern basin and from intermediate and deep waters of the western basin are opposite to that of the open ocean during glacial time 13c values were higher in intermediate and deep waters of the whole mediterranean and also in surface water of the eastern basin at the same time the 13c gradient of surface to deep waters was low this gradient increased during the last deglaciation while 13c values of g bulloides and benthic foraminifera decreased this decrease interrupted at 10 ka may have been related to increased fresh water run off from the bordering contintents due to increased precipitation especially in the tropical belt the 13c depletion is clearly recorded in the levantine and deep water masses and can be traced westward in the mediterranean outflow oxygen and carbon isotope anomalies recorded simultaneously in the east mediterranean by the shallow water species globigerinoides ruber during sapropel deposition indicate that increased precipitation on the bordering continents and strong fresh water run off during the time of the last deglaciation may have caused a density stratification and deep stagnation in the eastern basin uncertainties arise from the fact that in the mixing model deglacial mediterranean waters are mixed with continental fresh waters the isotopic characteristics of which are not entirely understood although increased surface water production of biogenic material can not be excluded as a possible cause of 13c depletion it appears that the river discharge including the nile as well as black sea input are also plausible sources for the fresh water layering

early messinian manganese deposition in ne cyprus related to cyclical redox changes in a silled hemipelagic basin prior to the mediterranean salinity crisis abstract unusual bedded manganese deposits occur within hemipelagic carbonates dated as early messinian 5 97 ma based on calcareous nannofossils these sediments accumulated during a time of increased isolation of the mediterranean sea from the atlantic ocean but prior to major sea level fall and evaporite precipitation during the messinian salinity crisis the manganese deposits form six main laterally continuous beds up to 70 cm thick compositionally they are dominated by poorly crystalline manganese oxide birnessite with associated mild enrichment in some trace elements e g ba ni cu mo as u background minerals include magnesian carbonate kaolinite chlorite mixed layer clays and talc serpentinite derived a tectonically controlled deep water basin existed to the south of a topographic ridge future kyrenia range in which seawater alternated between oxidising and oxygen depleted at depth orbital precession influenced the weathering of continental source areas that included basic igneous rocks and some pre existing hydrothermal deposits after entering the basin via land runoff manganese was retained in solution below the chemocline during stagnant low oxygen periods manganese oxide and associated trace elements e g mo u precipitated in response to cyclical seawater oxidation to form manganese rich layers up to layers with up to with up to c 30 mno to reach these very high concentrations soluble manganese may have fluxed upwards from an anoxic environment represented by early messinian sapropels manganese precipitation events diminished with time giving way to well oxygenated hemipelagic marl accumulation with a shelly infauna gypsum appears abruptly upwards above the marls in adjacent sections the mn deposition mainly represents an interplay between tectonically controlled basin formation chemically favourable source climatic conditions possible sea level change effects and likely diagenetic manganese enrichment the regional tectonic setting relates to early stage collision of the african and tauride eurasian plates

spatial productivity variations during formation of sapropels s5 and s6 in the mediterranean sea evidence from ba contents abstract we investigated five time equivalent core sections 180 110 kyr bp from the balearic sea menorca rise the easternmost levantine basin and southwest south and southeast of crete to reconstruct spatial patterns of productivity during deposition of sapropels s5 and s6 in the mediterranean sea our indicators are ba total organic carbon and carbonate contents we found no indications of ba remobilization within the investigated core intervals and used the accumulation rate of biogenic ba to compute paleoproductivity maximum surface water productivity up to 350 g c m2 yr was found during deposition of s5 isotope stage 5e but pronounced spatial variability is evident coeval sediment intervals in the balearic sea show very little productivity change suggesting that chemical and biological environments in the eastern and western mediterranean basins were decoupled in this interval we interpret the spatial variability as the result of two different modes of nutrient delivery to the photic zone river derived nutrient input and shoaling of the pycnocline nutricline to the photic zone the productivity increase during the formation of s6 was moderate compared to s5 and had a less marked spatial variability within the study area of the eastern mediterranean sea given that s6 formed during a glacial interval glacial boundary conditions such as high wind stress and or cooler surface water temperatures apparently favored lateral and vertical mixing and prevented the development of the spatial gradients within the eastern mediterranean sea ems observed for s5 a non sapropel sediment interval with elevated ba content and depleted 18o 16o ratios in planktonic foraminifer calcite was detected between s6 and s5 that corresponds to the weak northern hemisphere insolation maximum at 150 kyr at this time productivity apparently increased up to five times over surrounding intervals but abundant benthic fauna show that the deep water remained oxic following our interpretation the interval denotes a failed sapropel when a weaker monsoon did not force the ems into permanent stratification the comparison of interglacial and glacial sapropels illustrates the relevance of climatic boundary conditions in the northern catchment in determining the facies and spatial variability of sapropels within the ems

formation of mid chain alkane keto ols by post depositional oxidation of mid chain diols in mediterranean sapropels abstract a high resolution 1 3 cm sediment intervals organic geochemical study was carried out on the upper 50 60 cm of three box cores including the s1 sapropel from eastern mediterranean sea sediments the corg ba al and mn al depth profiles were used to define the oxidised and unoxidised part of the s1 sapropel post depositional oxidation affected ca 50 of the original sapropel in all three cores resulting in a significant drop in corg c30 long chain 1 15 diol and keto ols in the extracts of these sediments were quantified by gc ms the vertical variation of these biomarkers in the three cores showed a common depth profile the c30 long chain 1 15 diol occurs almost exclusively in the unoxidised sapropel the corresponding c30 long chain keto ol follows this depth profile although the keto ol concentrations in the unoxidised sapropel are much lower than the diol concentrations however the keto ol keto ol diol ratio shows a significant increase at the base of the oxidised sapropel this suggests that the long chain diol was transformed upon post depositional oxidation into the chemically related long chain keto ol and that this keto ol was subsequently further oxidised these findings indicate that long chain keto ols which have no reported biological source but occur ubiquitously in marine sediments may be formed by oxidation of long chain diols both in the water column and in the sediment

early diagenetic reactions in interbedded pelagic and turbiditic sediments in the nares abyssal plain western north atlantic consequences for the composition of sediment and interstitial water abstract measured pore water concentrations of iron in interbedded pelagic and turbiditic sediments from the nares abyssal plain are in excellent agreement with sediment colour and measured redox potential the organic carbon content of these sediments appears to define the redox conditions and consequently the porewater and solid phase concentration of constituents that are involved in early diagenetic reactions in the turbiditic sediments the concentration of no 3 generally goes to zero within a sediment depth of 1 m whereas at 8 m in a pelagic core from the same area the concentration of no 3 is still higher than it is in the bottom water the pore water concentration of mn 2 in the turbiditic sediments increases sharply down to a depth of approximately 3 m and from thereon remains nearly constant due to saturation with respect to mn ca co 3 the pore water of the turbiditic sediments is also saturated with respect to calcite the few diagenetic spikes in the pore water concentration of no 3 and mn 2 and the concentration depth profile of dissolved iron h 4 sio 4 and phosphate all clearly demonstrate the inhomogeneous nature of interbedded pelagic and turbiditic sediments the simultaneous occurrence of peaks of dissolved iron silica and of sediment intervals with a relatively high organic carbon content is attributed to enhanced early diagenetic reactions associated with the decomposition of organic matter in these specific intervals linked with these reactions is the irregular pore water concentration of phosphate which is shown to originate partly from the oxidation of organic matter but mainly from the desorption of phosphate from iron oxide potential concentrations of phosphate are calculated from the stoichiometric early diagenetic reactions and compared with measured concentrations due to the unique combination of low porosity and relatively high sedimentation rates the sediments from the nares abyssal plain are an ideal basis for the study of such interbedded sequences of pelagic and turbiditic deposits

diagenetic barium cycling in black sea sediments a case study for anoxic marine environments high resolution sedimentary records of major and minor elements al ba ca sr ti total organic carbon toc and profiles of pore water constituents view the mathml sourceso42 ch4 ca2 ba2 mg2 alkalinity were obtained for two gravity cores core 755 501 m water depth and core 214 1686 m water depth from the northwestern black sea the records were examined in order to gain insight into the cycling of ba in anoxic marine sediments characterized by a shallow sulfate methane transition smt as well as the applicability of barite as a primary productivity proxy in such a setting the ba records are strongly overprinted by diagenetic barite baso4 precipitation and remobilization authigenic ba enrichments were found at both sites at and slightly above the current smt transport reaction modeling was applied to simulate the migration of the smt during the changing geochemical conditions after the holocene seawater intrusion into the black sea based on this sediment intervals affected by diagenetic ba redistribution were identified results reveal that the intense overprint of ba and baxs ba excess above detrital average strongly limits its correlation to primary productivity these findings have implications for other modern and ancient anoxic basins such as sections covering the oceanic anoxic events which ba is frequently used as a primary productivity indicator our study also demonstrates the limitations concerning the use of baxs as a tracer for downward migrations of the smt due to high sedimentation rates at the investigated sites diagenetic barite fronts are buried below the smt within a relatively short period thus relict barite fronts would only be preserved for a few thousands of years if at all

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

post depositional migration of elements during diagenesis in brown clay and turbidite sequences in the north east atlantic abstract two cores from a ne atlantic pelagic clay area of low accumulation rate each contain a single turbidite with different age thickness and composition diagenesis following introduction of exotic turbidite material into the pelagic clay sequence has resulted in distinctive colour changes the diagenetic process is thought to be driven by bacterially mediated organic oxidation and compositional differences in the turbidites and clays allow examination of the effects on metal concentrations of this process in one core a long turbidite section emplaced 330 000 years ago is overlain by clay organic oxidation has apparently proceeded from the turbidite top downwards and has maintained a u concentration peak below the oxidation front marked by a colour change the u source is believed to be u initially associated with the organic matter in the oxidised section of the turbidite vanadium and cu behave similarly but upward migration of the redox sensitive metals mn and ni is also seen in the second core an 8 cm turbidite section was emplaced about 170 000 years ago in a clay column in this case organic consumption now appears complete but evidence for diagenetic effects is found in a 16 cm compositional alteration halo of the underlying pelagic clay fe ii has been enriched and the hydrogenous component of mn co ni and cu removed from the pelagic clay to form the halo

middle and late quaternary depositional sequences and cycles in the eastern mediterranean although most of the quaternary sediments of the eastern mediterranean appear reworked extensive areas of hemipelagic sediments occur mainly in the central part of the basin mediterranean ridge the most obvious character of these muddy sediments is the numerous changes in colour they result from the organic carbon content as well as from concentration and chemical form of metallic elements mn fe cu zn the succession of coloured layers is arranged into sequences developed between two sharp contacts a complete sequence involves five lithofacies from an oxidized layer at the base to a reduced sapropel at the top and displays progressive internal changes of colour from ochre beige greyish beige grey and black layers several sequence variants top truncated base truncated recurrent are identified these sequences are a consequence of changes in oceanographic conditions i e from oxidizing to reduced environments resulting in different organic and mineral contents based on detailed studies of quaternary sediments collected by coring a synthesized standard succession representative of the ordered sequences in the eastern mediterranean is proposed from about 650 000 yr as deduced from the calculated rate of sedimentation of 1 7 mm 1000yr 1 this succession appears modulated by cyclic events large scale periods 200 000 yr of reduced and oxidized sequences correlate with major alternate phases of flooding and reduced flow of the nile river during the quaternary subsequent sequences of shorter time scale 20 000 50 000 yr results from two factors heaviest monsoons leading to an increase of the influx of the nile river and global climatic changes eurasian ice sheet meltwater these two factors act synchronously or independently along the studied time span these interplaying factors result in periodic stages of increasingly restricted conditions in the basin and explain the complexity of the eastern mediterranean succession at least since 650 000 yr ago

control of sulfate pore water profiles by sedimentary events and the significance of anaerobic oxidation of methane for the burial of sulfur in marine sediments abstract gravity driven mass flow deposits proven by sedimentary and digital echosounder data are indicative for prevailing dynamic sedimentary conditions along the continental margin of the western argentine basin in this study we present geochemical data from a total of 23 gravity cores pore water so 4 is generally depleted within a few meters below the sediment surface by anaerobic oxidation of methane aom the different shapes of so 4 profiles concave kink and s type can be consistently explained by sedimentary slides possibly in combination with changes in the ch 4 flux from below thus mostly representing transient pore water conditions since slides may keep their original sedimentary signature a combined analysis and numerical modeling of geochemical physical properties and hydro acoustic data could be applied in order to reconstruct the sedimentary history we present first order estimates of the dating of sedimentary events for an area where conventional stratigraphic methods failed to this day the results of the investigated sites suggest that present day conditions are the result of events that occurred decades to thousands of years ago and promote a persisting mass transport from the shelf into the deep sea depositing high amounts of reactive compounds the high abundance of reactive iron phases in this region maintains low hydrogen sulfide levels in the sediments by a nearly quantitative precipitation of all reduced sulfate by aom for the total region we estimate a so 4 or ch 4 flux of 6 6 10 10 moles per year into the zone of aom projected to the global continental slope and rise area this may sum up to about 2 6 10 12 moles per year provided that the sulfur is completely fixed in the sediments it is about twice the global value of the recent global sulfur burial in marine sediments of 1 2 10 12 moles per year as previously estimated thus aom obviously contributes very significantly to the regulation of global sulfur reservoirs which is hitherto not sufficiently recognized this finding may have implications for global geochemical models as sulfur burial is an important control factor in the development of atmospheric oxygen levels over time

modes of sapropel formation in the eastern mediterranean some constraints based on pyrite properties abstract pyrite formation within and directly below sapropels in the eastern mediterranean was governed by the relative rates of sulphide production and fe liberation and supply to the organic rich layers at times of relatively high so2 4 reduction sulphide could diffuse downward from the sapropel and formed pyrite in underlying sediments the sources of fe for pyrite formation comprised detrital fe and diagenetically liberated fe ii from sapropel underlying sediments in organic rich sapropels input of fe from the water column via fe sulphide formation in the water may have been important as well rapid pyrite formation at high saturation levels resulted in the formation of framboidal pyrite within the sapropels whereas below the sapropels slow euhedral pyrite formation at low saturation levels occurred 34s values of pyrite are 33 to 50 below the sapropels 34s is lower than within the sapropels as a result of increased sulphide re oxidation at times of relatively high sulphide production and concentration when sulphide could escape from the sediment the percentage of initially formed sulphide that was re oxidized was estimated from organic carbon fluxes and burial efficiencies in the sediment it ranges from 34 to 80 varying significantly between sapropels increased palaeoproductivity as well as enhanced preservation contributed to magnified accumulation of organic matter in sapropels

redox zonation of elements at an oxic post oxic boundary in deep sea sediments abstract deep sea sediments generally provide limited evidence of redox control on the post depositional redistributions of elements this is because only a fraction of any element is reactive and observed elemental distributions are the result of a number of competing processes which are simultaneously active so that redox effects are not dominant a detailed investigation is reported of a core which is unusual in showing unequivocal evidence of direct redox control operating in a homogeneous environment that is relatively free from competing processes a progressive oxidation front has migrated slowly downwards into a uniform turbidite over a long period ca 250 ky the reactive fractions of several redox sensitive elements now show a remarkable degree of organisation around the redox boundary of this front with the different elements exhibiting individual responses solid phase enrichments are not coincident but are arranged in a clear succession of concentration peaks along the redox gradient from oxic to postoxic conditions the succession is mn i fe se and pt cu and pb v zn and sb and u the movement directions of most elements can be inferred from the peak shapes against the homogeneous turbidite background composition the system seems to have been essentially isolated within the sediment for most elements so that no loss or gain can be ascribed to redox processes exceptions are u and v which have been augmented by uptake from ocean bottom waters into the sediments by an efficient redox trap mechanism

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

sedimentary organic carbon to phosphorus ratios as a redox proxy in quaternary records from the mediterranean abstract in this study organic carbon to organic phosphorus c org p org and total phosphorus c org p tot ratios as bottom water redox proxies are explored for two eastern mediterranean sediment records extending back 600 700 kyrs cores kc19c 19 6 m long 2750 m water depth and kc01b 37 0 m long 3643 m water depth contain numerous organic rich layers sapropels throughout the two cores variations found in the c org p ratios correspond to those for other redox proxies such as total s contents and v al ratios accordingly these are interpreted as variations in bottom water oxygenation and inter sapropel redox variability in core kc19c the original c org p signals seem to have been preserved despite intense post depositional sulfidization high resolution p fractionation data of sapropel s5 from a third core ps25pc 3304 m water depth showing high and relatively stable c org p org ratios indicate that sapropel s5 at this deep location was deposited under permanently reducing conditions while p regeneration from organic matter was intense net p burial increased in the sapropel due to enhanced burial of inorganic calcium phosphate likely biogenic ca p sediment p contents and c org p tot ratios in s5 are variable reflecting short term changes in marine conditions productivity redox and sediment chemistry the c org p org and c org p tot ratios thus provide valuable insight into paleoceanographic conditions and pathways of p cycling for mediterranean sediment records extending back at least 600 700 kyrs

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

modification and complete removal of eastern mediterranean sapropels by postdepositional oxidation sapropels unusually dark organic rich sediment layers whose origin is controversial are widespread in the eastern mediterranean the upper surfaces of these layers appear sharp and show little evidence of bioturbation it has been suggested that postdepositional oxidation may have removed the dark coloration from the upper part of the original layer so that the top of the visible layer now lies somewhat below the original position of the sapropel top such a diagenetic alteration has considerable implications for the interpretation of the sedimentary record where the tops of dark layers are usually correlated with the cessation of sapropel formation geochemical data demonstrate that all visual evidence of a thin example of the most recent eastern mediterranean sapropel has been removed from the sedimentary record by oxidation processes such a process may have thinned all sapropel units by several centimetres the most recent period of sapropel formation probably ended as recently as 5 ka cf cited values between 6 0 and 7 6 ka

geochemistry of an exotic sediment layer above sapropel s 1 mud expulsion from the urania basin eastern mediterranean in a gravity core from the eastern mediterranean sea a chemically and mineralogically distinct 5 5 cm thick layer is present above sapropel s 1 and overlain by hemipelagic marls calcite is completely absent in this exotic layer dolomite is present only in small amounts and the cr concentrations are significantly enhanced the layer was deposited primarily under reducing conditions but the distributions of redox sensitive elements show that a large part of the exotic layer is now oxidised by a downward progressing oxidation front sediments from within the nearby anoxic hypersaline urania basin are similar to those from the exotic layer in particular in s c and o isotope distributions of pyrite and dolomite as well as increased cr concentrations mud expulsion due to expansion of gas rich mud is proposed to explain the presence of the exotic layer outside the urania basin the deposition of an anoxic layer above s 1 shielded the sapropel from oxidation which resulted in the rare occurrence of a complete preservation of s 1 and provides the first minimum age for the start of anoxic mud accumulation in the urania basin

reconstructing the seafloor environment during sapropel formation using benthic foraminiferal trace metals stable isotopes and sediment composition the evolution of productivity redox conditions temperature and ventilation during the deposition of an aegean sapropel s1 is independently constrained using bulk sediment composition and high resolution single specimen benthic foraminiferal trace metal and stable isotope data the occurrence of benthic foraminifer hoeglundina elegans h elegans through a shallow water 260 m sapropel permits for the first time a comparison between dissolved and particulate concentrations of ba and mn and the construction of a mg ca based temperature record through sapropel s1 the simultaneous increase in sedimentary ba and incorporated ba in foraminiferal test carbonate ba ca h elegans points to a close coupling between ba cycling and export productivity during sapropel deposition sedimentary mn content mn al sed is reduced corresponding to enhanced mn2 mobilization from sedimentary mn oxides under suboxic conditions the consequently elevated dissolved mn2 concentrations are reflected in enhanced mn ca h elegans levels the magnitude and duration of the sapropel interruption and other short term cooling events are constrained using mg ca thermometry based on integrating productivity and ventilation records with the temperature record we propose a two mode hysteresis model for sapropel formation

long eccentricity cycle in pliocene oceanic carbon reservoir a comparison between the mediterranean and the south china sea abstract as quantitative paleoclimate time series extend deeper into the geological past growing evidence indicates the extensive occurrence of the 400 kyr long eccentricity cycle in geological records the long cycles are best manifested in the marine carbon isotope as a series of 13 cmax which correspond to the long eccentricity s minima however it remains unclear how eccentricity affects the oceanic carbon reservoir to determine what processes are involved in generating the 400 kyr cycles one long eccentricity cycle in the late pliocene from 3 2 myr to 2 8 myr was examined in two sections respectively from the mediterranean and the south china sea the results indicate that the mediterranean section displays distinct precession cycles in all of the studied proxy time series and their amplitudes are modulated by eccentricity whereas the precession cycles and the eccentricity modulation are much weaker in the proxy sequences from the south china sea the difference is attributed to the fact that african monsoon was overwhelmingly dominated by precessional forcing and the mediterranean basin was isolated from glacial induced reorganizations of the global ocean whereas totally different conditions existed in the south china sea it may be inferred from the comparison that the 13 cmax originated largely from the global ocean and was unlikely caused by local basin factors at the long eccentricity maximum summer insolation reached a maximum at low latitudes and the intensified global monsoon changed the ocean carbon reservoir and the 13 c value because of the long residence time of carbon in the ocean 13 c changes in the global oceanic reservoir primarily occur on a 10 5 yr time scale with a smoothing effect in the lower frequencies the 400 kyr long eccentricity was pervasive at least in the cenozoic ocean but its expression was subject to spatio temporal variations particularly under the influence of the ice sheet development

geochemistry of hydrothermal mn oxide deposits from the s w pacific island arc abstract hydrothermal mn oxide crusts have been removed from the tonga kermadec ridge the first such hydrothermal deposits to be reported in the s w pacific island arc in several respects the deposits are similar to hydrothermal mn crusts from oceanic spreading centre settings they are limited in areal extent comprise well crystalline birnessite and generally display extreme fractionation of mn from fe they are strongly depleted in many elements compared to hydrogenous mn deposits but are comparatively enriched in li zn mo and cd the group ia and group iia metals show strong intercorrelations and the behaviour of mg in the purest samples may indicate the extent to which normal seawater has influenced the composition of the deposits certain aspects of the deposits are not typical of hydrothermal mn deposits in particular at least some of the crusts have developed on a sediment or unconsolidated talus substrate some crusts or specific layers within some crusts display a chemical composition which suggests a significant input from normal seawater

a new geochemical classification of sedimentary environments because of the relative constancy of ph in most subaqueous sediments and the general lack of measurability of eh these parameters are not practically useful for classifying sedimentary environments in their place a new classification is offered which derived from studies of modern sediments is based on the presence or absence of dissolved oxygen and dissolved sulfide in the sediments at the time of authigenic mineral formation sedimentary environments are first of all divided into oxic and anoxic depending upon the presence or absence of measurable dissolved oxygen anoxic environments in turn are divided into sulfidic and non sulfidic depending upon the presence of measurable dissolved sulfide anoxic nonsulfidic environments are further divided into postoxic or resulting from oxygen removal without sulfate reduction weakly reducing and methanic or resulting from complete sulfate reduction with consequent methane formation strongly reducing the environments are shown to succeed one another during early diagenesis in the order oxic post oxic sulfidic methanic iron and manganese minerals characteristic and stable in each environment are listed and discussed so that they may be used to distinguish the environments when studying the ancient geological record

active post depositional oxidation of the most recent sapropel s1 in sediments of the eastern mediterranean sea abstract over a wide area of the eastern mediterranean basin two mn rich layers have been observed above the most recent sapropel s1 one immediately above the sapropel top and one a few centimetres closer to the sediment surface different mechanisms have been proposed to explain the occurrence of these two mn peaks either both peaks have a diagenetic origin in which case the upper mn peak is actively forming or the lower peak is actively forming and the upper peak has a different formation mechanism high resolution porewater including a gel sampler used for the first time in marine sediments and solid phase data are now used to demonstrate that the oxidation front is located at the level of the lower mn peak which therefore is presently being formed a barium organic carbon relationship is used to calculate the initial organic carbon profile of the s1 sapropel the palaeoproductivity profiles generated by this method demonstrate that the original sapropel unit was bounded by the upper mn peak this implies that the interval between the two mn peaks where a low organic carbon content is now observed was originally part of the sapropel the initially deposited organic carbon has been oxidised by a progressive downwards moving oxidation front the penetration depth of this oxidation front i e the distance between the two mn peaks is mainly determined by the organic carbon content the sediment accumulation rate and the bioturbation depth the upper mn peak appears to have formed as a result of either mn precipitation upon oxygenation of previously anoxic eastern mediterranean deep water or preservation of a surficial mn peak at the end of the high productivity episode in either case the upper mn peak marks the end of sapropel formation as indicated by the ba profiles this means that formation of the s1 sapropel ceased more recently than is indicated by radiocarbon dating of the visible top of s1

particle mixing rates in sediments of the eastern equatorial pacific evidence from 210pb 239 240pu and 137cs distributions at manop sites abstract particle mixing rates db calculated from excess 210pb gradients in sediments of the east equatorial pacific range from 0 04 to 0 5 cm2 y with variation of a factor of 3 4 at a single site diffusion of the 236ra daughter 222rn may affect 210pb distributions under conditions of slow mixing and low 210pb flux to the seafloor as shown by a siliceous ooze clay core which contained the fallout radionuclides 239 240pu and 137cs but no excess 210pb relative to 226ra there is no clear relationship between 210pbderived mixing rates and sediment type accumulation rate or organic carbon flux to the sediments comparison of 210pb mixing rates with those calculated from 239 240pu and 137cs distributions reveals better agreement for a pulse input of the fallout radionuclides db 0 03 0 4 cm2 y than for continuous input at a constant rate db 0 1 1 6 cm2 y although the pu and 137cs data are better fit by the latter model the agreement may be fortuitous because 239 240pu and 137cs appear significantly deeper than 210pb in at least one core tracer separation could be caused by particle size selective mixing by the benthic fauna or by chemical mobilization if the fallout radionuclides are scavenged from surface waters by large organic rich particles such as fecal pellets their release and migration may result from decomposition of the carrier in surface sediments either a relatively unreactive form of pu e g oxidized pu has been released by this process or a one dimensional model is inadequate to explain its observed penetration into the sediments activity ratios of 239 240 pu 137 cs in the sediments decrease with increasing north latitude and the trend reflects higher fluxes of 239 240pu near the weapons test site at christmas island 2 n the 239 240 pu 137 cs ratios and fluxes to the sediment assuming constant input at the siliceous ooze red clay site are consistent with published sediment trap data from a nearby site thus if fallout radionuclide fluxes to the sea floor were higher in the past both 239 240pu and 137cs have been released from sinking particles

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

the tempo of holocene climatic change in the eastern mediterranean region new high resolution crater lake sediment data from central turkey this study presents results from a multi proxy analysis of cores taken in a crater lake sequence from eski acigol in central turkey which cover the period from pre c 16000 cal yr bp to the present the sediments comprise an upper unit of generally non laminated banded to massive silts and peats of mid to late holocene age overlying a laminated unit of late pleistocene to early mid holocene age the laminae comprising mainly aragonite amorphous silica diatom frustules and organic matter were formed in a relatively deep dilute meromictic lake pollen data indicate an abrupt replacement of artemisia chenopod steppe by grass oak terebinth parkland during the period of laminae deposition marking the start of the holocene a gradual increase in tree pollen during the early holocene came to an end c 6500 cal yr bp u series and adjusted c 14 timescale when mesic deciduous taxa declined at the same time as lake levels fell human impact on regional vegetation is inferred from a sharp decline in oak around 4500 4000 cal yr bp diatom isotopic and mineralogical data indicate that during the second half of the holocene the lake became relatively shallow and oscillated between fresh and brackish evaporated water conditions the contrast between wetter early and drier late holocene climatic conditions is matched by other eastern and central mediterranean proxy climate data while the eski acigol sequence resembles holocene hydroclimatic changes in the saharo arabian zone and was also apparently linked to orbital forcing it is unlikely to have had the same direct cause i e an expansion and subsequent retreat of monsoon rainfall

coccolithophore productivity response to greenhouse event of the paleocene eocene thermal maximum abstract during the paleocene eocene thermal maximum petm rapid release of isotopically light c to the ocean atmosphere system elevated the greenhouse effect and warmed temperatures by 5 7 c for 105 yr the response of the planktic ecosystems and productivity to the dramatic climate changes of the petm may represent a significant feedback to the carbon cycle changes but has been difficult to document we examine sr ca ratios in calcareous nannofossils in sediments spanning the petm in three open ocean sites as a new approach to examine productivity and ecological shifts in calcifying plankton the large heterogeneity in sr ca among different nannofossil genera indicates that nannofossil sr ca reflects primary productivity driven geochemical signals and not diagenetic overprinting elevated sr ca ratios in several genera and constant ratios in other genera suggest increased overall productivity in the atlantic sector of the southern ocean during the petm dominant nannofossil genera in tropical atlantic and pacific sites show sr ca variations during the petm which are comparable to background variability prior to the petm despite acidification of the ocean there was not a productivity crisis among calcifying phytoplankton we use the pandora ocean box model to explore possible mechanisms for petm productivity change if independent proxy evidence for more stratified conditions in the southern ocean during the petm is robust then maintenance of stable or increased productivity there likely reflects increased nutrient inventories of the ocean increased nutrient inventories could have resulted from climatically enhanced weathering and would have important implications for burial rates of organic carbon and stabilization of climate and the carbon cycle

sedimentation and formation of secondary minerals in the hypersaline discovery basin eastern mediterranean two cores recovered from the discovery basin and one reference core from a location outside the basin were investigated in detail in order to decipher the influence of hypersaline brines on sediment geochemistry the cores contain a tephra layer presumable y 5 and carbonate microfossils which permit a tentative chrono and lithostratigraphic correlation a layer containing up to 60 wt biogenic opal and 6 6 wt organic carbon was identified in one basin core which probably represents the best preserved example of eastern mediterranean sapropel s 1 the basin is filled with a concentrated solution of mgcl2 which is enriched in dissolved sulfate and has the highest salinity ever encountered in the marine environment pore water profiles demonstrate that this brine dissolves sedimentary calcite to form secondary carbonate and sulfate bearing minerals of these dolomite magnesite and gypsum were identified by x ray diffractometry thermodynamic calculations show that these phases form in equilibrium with the anomalous brine composition

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

organic geochemical evidence of late glacial holocene climate instability in the north aegean sea sedimentary molecular biomarker compositions organic carbon and caco3 concentrations and bulk organic 13c and total 15n values document a series of paleoclimatic changes that have affected organic matter production and sedimentation in the north aegean sea from the termination of the latest glacial maximum through the middle holocene continental environmental conditions have been inferred from land plant biomarkers paleoproductivity patterns of diatoms prymnesiophytes dinoflagellates and nannoplankton were discerned from marine derived biomarkers although organic matter is predominantly marine variations in the proportion of marine and land contributions and in its general preservation are evident rapid changes in the eastern mediterranean thermohaline circulation evidently occurred in parallel to sea surface temperature oscillations enhanced deep water ventilation accompanied cold intervals in the late last glacial the younger dryas and during an interruption of deposition of the s1 sapropel probably in response to strengthening of north winds over the region in contrast decreased thermohaline circulation occurred during the warm interval associated with the s1 sapropel during this period increased freshwater inputs diminished ventilation of deep water masses and enhanced organic matter production and preservation intriguing fluctuations in sea surface temperatures and the concentrations of marine and terrestrial biomarkers within the sapropelic layer most prominently in the interruption from 8 2 to 7 8 calibrated radiocarbon conventional kyr bp support the hypothesis that several distinct events of deep water reoxygenation occurred in the north aegean sea during deposition of the s1 sapropel these events reflect centennial excursions to the more common low productivity and well ventilated conditions of the mediterranean that may possibly be related to north atlantic oscillation cycles

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

redox sensitivity of p cycling during marine black shale formation dynamics of sulfidic and anoxic non sulfidic bottom waters abstract a high resolution geochemical record of a 120 cm black shale interval deposited during the coniacian santonian oceanic anoxic event 3 odp leg 207 site 1261 demerara rise has been constructed to provide detailed insight into rapid changes in deep ocean and sediment paleo redox conditions high contents of organic matter sulfur and redox sensitive trace metals cd mo v zn as well as continuous lamination point to deposition under consistently oxygen free and largely sulfidic bottom water conditions however rapid and cyclic changes in deep ocean redox are documented by short term 15 20 ka intervals with decreased total organic carbon toc s and redox sensitive trace metal contents and in particular pronounced phosphorus peaks up to 2 5 wt p associated with elevated fe oxide contents sequential iron and phosphate extractions confirm that p is dominantly bound to iron oxides and incorporated into authigenic apatite preservation of this fe p coupling in an otherwise sulfidic depositional environment as indicated by fe speciation and high amounts of sulfurized organic matter may be unexpected and provides evidence for temporarily non sulfidic bottom waters however there is no evidence for deposition under oxic conditions instead sulfidic conditions were punctuated by periods of anoxic non sulfidic bottom waters during these periods phosphate was effectively scavenged during precipitation of iron oxyhydr oxides in the upper water column and was subsequently deposited and largely preserved at the sea floor after 15 25 ka sulfidic bottom water conditions were re established leading to the initial precipitation of cds zns and pyrite subsequently increasing concentrations of h2s in the water column led to extensive formation of sulfurized organic matter which effectively scavenged particle reactive mo complexes thiomolybdates at site 1261 sulfidic bottom waters lasted for 90 100 ka followed by another period of anoxic non sulfidic conditions lasting for 15 20 ka the observed cyclicity at the lower end of the redox scale may have been triggered by repeated incursions of more oxygenated surface to mid waters from the south atlantic resulting in a lowering of the oxic anoxic chemocline in the water column alternatively sea water sulfate might have been stripped by long lasting high rates of sulfate reduction removing the ultimate source for hs production

geochemistry of eastern mediterranean sediments primary sediment composition and diagenetic alterations abstract two cores recovered in the eastern mediterranean were analysed for major minor and trace elements the primary chemical composition of the sediment is different at each location probably because the lithological sources and the relative biogenic contributions differ carbonates are important for the concentration of ca mg and sr whereas aluminosilicates determine the concentration of si al k li y and be and to a lesser extent that of fe cr ti mg zn and zr in sapropels organic carbon and sulphur seem to be closely related bromine mo p fe v cu zn co ni and cr are closely associated with organic and sulphidic compounds the concentration versus depth profile for organic carbon in two sapropels points to a rapid establishment of conditions that gave rise to sapropel formation followed by a gradual transition back to normal conditions the primary composition is overprinted by diagenetic processes sulphate reducing conditions occurred during and just after sapropel deposition a progressive oxidation front mechanism which became active after sapropel deposition is responsible for additional major geochemical changes this diagenetic phenomenon has strong implications for the chemistry of fe mn ni co zn cu cr v u as and sb

an analytical solution to separate p waves and s waves in vsp wavefields an analytical solution to separate p waves and s waves in vertical seismic profile vsp wavefields is derived using combinations of certain terms of the formal solution for forward vsp modeling some practical applications of this method to synthetic seismograms and field data are investigated and evaluated little wave distortion is recognized and the weak wavefield masked by dominant wavetrains can be extracted with this method the decomposed wavefield is expressed in the frequency depth f z domain as a linear combination of up to the third order differential of traces which is approximated by trace differences in the practical separation process in general five traces with single component data are required in this process but the same process is implemented with only three traces in the acoustic case two trace extrapolation is applied to each edge of the data gather to enhance the accuracy of trace difference since the formulas are developed in the f z domain the influence of anelasticity can be taken into account and the calculation is carried out fast enough with the benefit of the fast fourier transform fft

geochemistry and mineralogy of the nw aegean sea surface sediments implications for river runoff and anthropogenic impact abstract surface sediments of the nw aegean sea were analyzed for clay mineral composition 94 samples organic c and carbonate content and major and minor elements 112 samples illite is the most abundant clay mineral followed by smectite chlorite and kaolinite clay minerals are preferentially deposited within the continental shelf and slope environment due to the prevailing cyclonic circulation and the formation of flocs in the rivers pro delta areas the spatial distribution of major lithogenic elements si al ti fe is substantially biased by the presence of relict sands located in the central eastern part of the thermaikos gulf continental shelf biogenic elements ca sr are noticeably pronounced on the northern flank of the north sporades islands organic c content and minor elements cu zn as and pb are enriched markedly over the thessaloniki bay and gulf suggesting substantial human impact deriving largely from untreated or partly treated domestic and industrial effluents the terrigenous component of the elements is preferentially contributed from the axios river zn and pb the aliakmon river cr co ni cu and as and to a lesser extent from the pinios river v co ni and cu a considerable part of the metals originates in ultra mafic and volcanic formations which are abundant in the rivers catchment basins carbonate content exhibits great variability with the highest values observed in biogenic sediments of the sporades basin in the latter area mn and fe oxides and hydroxides were found as coatings on calcite the coatings were enriched in cr co ni zn as mo and pb due to adsorption or ion exchange during early diagenesis the combined influence of the river systems the thessaloniki metropolis and the diverse sedimentological background generates great patchiness in the distribution of major and minor elements

shipboard routine and pressure filtration system for pore water extraction from suboxic sediments abstract a shipboard working procedure for the handling and porewater extraction of suboxic sediments is outlined in addition a detailed description is given of the shipboard pressure filtration system that has been used to extract porewater this procedure in combination with the pressure filtration system has been demonstrated to produce reliable porewater from suboxic sediments

pelagic productivity changes in the equatorial area of the northwest indian ocean during the last 400 000 years abstract major and selected trace element al fe mg k ba p mn v cu ni and ti records were analyzed in two cores recovered from the northwestern indian ocean core md 90940 on the madingley rise and core md 85668 in the somali basin in order to monitor the sedimentary response to pelagic productivity in this area during the last 400 000 years geochemical proxies such as bulk mass accumulation rate mar al normalized major and trace element contents major and trace element mars were compared to biologic markers of palaeoproductivity a new radiolarian index rad ratio and the variations of foraminiferal and radiolarian assemblages special attention being paid to the barium record a sequential leaching procedure determined the main ba carrier fraction in the sediment and thus the amount of biogenic barium the blue ocean sedimentation on the madingley rise core md 90940 is characterized by a low mar and an insignificant terrigenous input the bulk mar variations are directly related to the variations of the rad ratio reflecting a direct link between surface productivity and pelagic sedimentation at this site in this sediment barium is mainly found as barite and can be considered as a palaeoproductivity proxy in the somali basin core md 85668 the terrigenous inputs are relatively higher but the bulk mar variations are still related to the variations of surface productivity no barite was found and barium is mainly linked to the terrigenous input a comparison of the two pelagic sites of the madingley rise and the somali basin points out the differences between the barium records at both sites despite the location of both cores in the pelagic domain the geochemical record and especially the barium one is different from one core to the other the comparison of the variations of the bulk mar which reflects the variations of the surface productivity presents significant discrepancies between both sites in the blue ocean core md 90940 the productivity peak values are mainly recorded during glacial intervals but their maximum values are observed during interglacial isotope stage 9 in the somali basin core md 85668 high bulk mar periods occurred during glacial isotope stages the interglacial episode of high productivity recorded on the madingley rise the absence of significant variations of productivity at the 8 7 transition in the somali basin as well as the absence of a time lag between both records indicate that the surface productivity is in this area controlled more by the local variations of the palaeoceanographic patterns than the global climatic changes e g the glacial interglacial alternations

microelectrode studies of organic carbon degradation and calcite dissolution at a california continental rise site fine scale porewater profiles of resistivity o2 ph and pco2 were measured in situ with microelectrodes at a site on the california continental rise they are reported here with more traditional measurements of shipboard porewater no3 alkalinity and tco2 and sediment organic c and caco3 profiles a numerical model encompassing diffusion advection and multiple reaction terms is applied to these data to characterize organic carbon degradation and caco3 dissolution processes near the sediment water interface a benthic o2 flux of 58 mol cm 2 yr 1 over the top 1 mm sediment is estimated based on one measured sub mm depth scale o2 profile the numerical model indicates that this high o2 consumption rate is related to a very labile fraction of organic c which has a degradation rate constant of approximately 4 5 10 8 s 1 1 4 yr 1 and which is not mixed downward by biological mixing seasonality in the benthic o2 consumption rate of this site may be attributed to variations in the input rate of this highly labile organic c degradation rate constants of the bulk organic c by oxygen reduction and by nitrate reduction are estimated to be about the same 1 10 9 s 1 the organic c rain rate responsible for the bulk organic c is estimated to be 53 mol cm 2 yr 1 this estimate exceeds the average rain rate determined by sediment trap collections at this site saturation state profiles calculated from the in situ ph and pco2 data and from modelling the in situ o2 and ph data both indicate that the porewater is undersaturated with respect to calcite to a depth of at least 8 cm the dissolution rate constant of calcite in this caco3 poor station is determined to be 5 10 day 1 assuming the reaction order is 4 5 which is close to the minimum estimates for environments richer in calcite a uniform calcite dissolution rate constant therefore may be adequate for representing carbonate dissolution in global scale models of ocean chemistry

redistribution and geochemical behaviour of redox sensitive elements around s1 the most recent eastern mediterranean sapropel the youngest eastern mediterranean sapropel s1 is generally believed to have formed 7 9 14c ky b p the distribution of redox sensitive elements above in and below the sharply defined organic rich unit reveal that s 1 has already suffered heavy diagenetic alteration its present thickness based on its dark colour is only a fraction of its original thickness in one core visual evidence of s1 with an inferred initial thickness of 6 cm has been destroyed and a similar thickness appears to have been lost from the tops of another two examples this is caused by oxidation of the upper reaches of s 1 by a progressive oxidation front which commenced 5 2 5 4 14c ky ago and still appears to be active in the three cores studied diagenetic relocation of many redox sensitive elements has occurred most elements expected to be enriched in sapropels or sulphide rich sediments already have maximum concentrations above or below rather than in the present s 1 layers similarities are observed in the geochemical behaviour of as fe and p of co cu mn ni and zn and of cd mo sb ti u and v the behaviour of ba is distinctive and its immobility as barite makes it an indicator for palaeoproductivity and the original high s1 corg content the elements se and i exhibit particularly large sharp concentration peaks and together are proposed as useful indicators of the present boundary between oxic and post oxic conditions

early organic diagenesis the significance of progressive subsurface oxidation fronts in pelagic sediments abstract porewater and solid phase geochemical data at two contrasting ne atlantic stations are reported station 10552 on the cape verde abyssal plain is a site of slow pelagic accumulation ca 0 4 cm kyr 1 molecular oxygen is present in the sediment column to at least 2 m and probably much deeper labile organic carbon is almost totally consumed in the upper few centimetres of the sediment by contrast at station 10554 on the madeira abyssal plain the pelagic sequence has been interrupted by the occasional deposition of organic rich turbidites porewater oxygen and nitrate profiles show that subsurface organic metabolism of the organic carbon associated with the uppermost turbidite layer is a significant fraction of the overall metabolism in the sediment column this metabolism occurs at a relatively thin reaction front which progresses deeper into the turbidite with time this phenomenon exerts a controlling influence on the present nutrient profile and redox succession in a less extreme form substrate distributions of this latter type are not uncommon in atlantic sediments a model has been developed which is controlled by both oxygen and nitrate data this model permits a vertical profile of metabolic activity to be derived and also gives estimates of the reaction rate constants and solid phase mixing rates at these two contrasting stations about 30 of the total activity at station 10554 is located within the turbidite at the deepening reaction front this is a non steady state condition in fact it is found that the integrated metabolic activity at the two stations is not dissimilar ca 1 2 10 13 moles cm 2 sec 1 the striking differences in redox profile are therefore primarily attributable to differences in the distribution of metabolic activity within the column

the diagenetic formation of metal rich layers in sapropel containing sediments in the eastern mediterranean two cores recovered from different locations in the eastern mediterranean contain intercalations of organic rich sapropels in organic poor hemipelagic sediments in both cores enrichments of mn and fe were found in the oxidised section of the sediment above the sapropel s1 the sediments followed a diagenetic cycle which began after the sapropel formation finished about 7000 years ago first during a non steady state diagenetic phase metal rich layers were formed at a downward moving oxidation front the front decelerated at the top of the sapropel as a consequence of increasing amounts of corg and sulphides that had to be oxidised during the second part of this non steady state phase the oxidation front starts moving upwards with respect to the sapropel manganese is remobilised in preference to iron due to thermodynamics reinforced by kinetics when the upward movement of the oxidation front becomes equal to the sedimentation rate steady state is established with respect to the new organic poor sedimentary circumstances at location 31g1 the system is at or close to steady state at location 9g1 however this steady state phase has never been reached between 1900 and 1350 years bp the organic carbon accumulation rate probably increased suddenly inducing a retreat of the oxidation front and the non steady state formation of double peaks

diagenetic pyritisation under eastern mediterranean sapropels caused by downward sulphide diffusion recurrent organic rich layers sapropels in eastern mediterranean sediments are enriched in corg fe and s sulphur and fe are enriched in a zone immediately below the sapropels whereas corg is not 34s values of bulk sediments and simple mass balance calculations indicate that so42 reduction has taken place in an open system with all hs formed at or close to the sediment surface formation of pyrite in the sapropel was fe limited and consequently excess hs was able to migrate downwards downward sulphidisation this resulted in the formation of pyrite below the sapropel by reaction of this hs with solid phase ferric iron and fe2 diffusing upwards from underlying sediments the fe2 source probably includes fe hydr oxide layers formed at former oxidation fronts above previously deposited and buried sapropels this downward sulphidisation mechanism allows accumulation of twice as much s in alternating organic rich anoxic organic poor suboxic sediments compared to what is preserved in organic rich anoxic sediments

magnetic properties and geochemistry of the active oxidation front and the youngest sapropel in the eastern mediterranean sea summary magnetic properties irm arm xin s ratio at 0 3 t room temperature rt hysteresis and thermomagnetic curves and geochemical data fe s mn al ti organic c were studied in two eastern mediterranean boxcores abc26 and bc19 at a resolution of 3 5 mm the boxcores contain sapropel s1 9 6 kyr bp at a few decimetres below seafloor the magnetic fraction consists predominantly of single domain sd to pseudo singledomain psd magnetite in the entire cores the original input of magnetic grains comes from two sources aeolian dust both cores and volcanic ash from the minoan eruption of santorini core bc19 only non steady state diagenesis has changed the magnetic mineralogy considerably in these alternating organic rich organic poor sediments during deposition of sapropel s1 reductive diagenesis and pyritization in and just below the sapropel caused lower magnetic intensities coarser magnetic grain sizes and partial maghemitization in thermomagnetic curves two types of pyrite can be identified one oxidizes below 450 uc and the other above 450 uc the higher oxidation temperature is predominantly found below the sapropel this may be related to the microtexture of pyrite which is euhedral below sapropels and mainly framboidal within sapropels since the end of sapropel deposition a downward moving oxidation front has oxidized the upper half c 5 cm of the sapropel the oxidized part of the sapropel is enriched in diagenetically formed fe oxides with relatively high coercivity and arm the maximum coercivity is found in a distinct layer between the present day mn and fe redox boundaries at the top of the unoxidized sapropel the freshly precipitated fe oxides in this centimetre thick layer contain a mixture of superparamagnetic sp grains and high coercivity sd magnetite higher in the oxidized zone the freshly precipitated fe oxides have aged into generally slightly lower coercivity sd grains with relatively high arm in addition to the diagenetic formation of fe oxides at the top of the sapropel formation of a ferrimagnetic fe monosulphide may have occurred within the sapropel during later stages of diagenesis which may have enhanced the arm signal in the organic rich interval in particular

combined organic and inorganic geochemical reconstruction of paleodepositional conditions of a pliocene sapropel from the eastern mediterranean sea layers of organic carbon rich sapropels in the sediment record of the mediterranean sea give evidence of repetitive changes in regional plio pleistocene climate results from biomarker molecule and major and trace element analyses of closely spaced samples are used to reconstruct the conditions leading to deposition of a pliocene sapropel at ocean drilling program odp site 969 on the mediterranean ridge organic carbon concentrations increase from 0 2 outside the sapropel and peak to more than 30 within it major and trace elemental composition and biomarker derived parameters indicate elevated productivity depletion of water column dissolved oxygen content and changes in sediment provenance in response to climatic changes budgets of rhenium thallium and other trace metals indicate that deep water exchange between the mediterranean subbasins and the atlantic ocean was not completely interrupted during sapropel formation enrichment factors of redox sensitive and sulfide forming trace metals as well as the presence of isorenieratene derivatives and high stanol sterol ratios point to an extended zone of anoxic water masses depth profiles of biomarker compositions sterols long chain alkenones alkandiols and ketols fatty acids indicate great floral diversity during deposition of a single sapropel and highlight the sensitive response of the marine community to variable environmental conditions changes in water mass circulation and eolian transport can be reconstructed by use of both lithogenic elements and average chain lengths of n alkanes acl index

influence of an organic poor landslide deposit on the early diagenesis of iron and manganese in a coastal marine sediment sediments and porewaters were subsampled from two box cores collected at 135 m depth on the landward slope of the largest basin of the saguenay fjord quebec canada the saguenay fjord sediments are composed mostly of eroded glaciomarine clays surrounding the fjord area the sediments contain relatively large concentrations of organic carbon and are sulfidic a few millimeters below the sediment water interface they are characterized by anomalously high hg concentrations and acid volatile sulfide avs pyrite ratios the vertical distribution of total hg concentrations in the sediments can be correlated to the organic matter content and an anthropogenic source the high avs pyrite ratios reflect conditions conducive to preservation of fe monosulfides in 1971 a catastrophic landslide resulted in the displacement and transport of 6 9 106m3 of post wisconsinian marine clay into the saguenay fjord the landslide material was deficient in organic carbon and anthropogenic hg relative to the indigenous sediment subsequent to burial the landslide deposit influenced the migration and deposition patterns of mobilizable elements acting alternatively as a sink and a source of reduced fe and mn as the redox boundary migrated through it nonsteady state sulfate reduction rates were established due to the nonuniform distribution of organic carbon with depth iron sulfide peaks reflect this distribution and the position of the relict redox boundary manganese remobilization was apparently unaffected by the deposition of the landslide layer and reduced mn migrated freely to the redox boundary a schematic representation of the sequence of diagenetic events which led to the postdepositional remobilization of fe and mn and the migration of the oxidation front following the deposition of the landslide material is proposed

accumulation of barium in recent skagerrak sediments sources and distribution controls abstract geochemical and mineralogical methods have been applied to document the ba and barite distributions in the skagerrak sediments barite released in the central north sea during hydrocarbon drilling as a component of the drilling mud is a principal carrier of ba in the recent skagerrak sediments the systematic pattern of the surface ba contents displaying a generally decreasing trend from south to north is consistent with the barite transport from the north sea towards the skagerrak the predominant barite grain size ranges between 10 and 20 m the sub surface ba distribution is characterised by the elevated contents within the top 5 10 cm which downward is followed by uniformly low contents considering the sedimentation rate the start of sub surface ba enrichment generally corresponds to the late 1960s coinciding with the beginning of off shore drilling in the north sea in addition to the primary depositional factors controlling the shallow stratigraphic ba distribution the influence of diagenetic processes is suggested by the dissolution features on the barite grain surfaces and the profile relationships to the interpreted diagenetic zones

a hydrothermal manganese deposit from the eratosthenes seamount eastern mediterranean sea abstract a manganese crust horizon is described from the eratosthenes seamount south of cyprus in the eastern mediterranean sea its morphological and geochemical features coupled with its geotectonic setting suggest that submarine hydrothermal activity is responsible for its formation

redistribution of trace metals in a mineralized spodosol due to weathering liikavaara northern sweden the till east of the liikavaara ostra ore deposit in northern sweden is in some parts rich in cu and other sulphide associated metals groundwater flowing in this till has higher concentrations of cu than groundwater in a reference area where the till has low concentrations of cu and other metals to understand the processes that release metals from the mineralized till at liikavaara into the groundwater the authors performed a detailed study of the 2 mm fraction of a till profile where the highest metal concentrations in the liikavaara area occur the geochemistry and mineralogy of the till were determined and the soil water was sampled by tension lysimeters the importance of local diffusion of cu bearing airborne dust from the adjacent aitik mine tailings impoundment was quantified and solid speciation of metals in airborne material was performed by sequential extraction the results from liikavaara were compared to results from the reference area glacial ice picked up sulphide rich material from the liikavaara ostra cu ore during its flow this material was deposited in the till east of the ore body when the ice melted the sulphides have been dissolved in the 2 mm fraction during 8 7 ka of weathering since the glacial ice retreated after dissolution of the sulphides cu was redistributed and secondarily retained in association with fe oxyhydroxides and altered biotite other sulphide associated elements such as co ni and zn show the same pattern in the till profile as cu though the concentrations are much lower uptake of cu2 in the biotite through ion exchange with k may be an important mechanism for cu enrichment in biotite at liikavaara the airborne dust is not the source of cu in the till although the soil water at liikavaara has higher concentrations of cu and other metals than the soil water at the reference area the cu concentration is too low for infiltrating soil water to explain the high cu concentrations observed in groundwater the high metal concentrations in the till of cu in particular cause the increased concentrations in the local groundwater a fluctuating groundwater table washes out cu and other metals from the till it is possible that increased cu concentration in the local groundwater is caused by dissolved organic complexes or by colloids 0 45 m rich in organic matter and or fe oxyhydroxides

a mediterranean perspective on 10be sedimentation and climate around the matuyama brunhes boundary les liaisons dangereuses abstract the 10be 9be ratio is commonly employed as a tool for establishing the stratigraphic position of paleomagnetic excursions and reversals whenever the traditional paleomagnetic approach fails to provide conclusive results in particular it is held that 10be production rates in the atmosphere depend on the strength of the earth s magnetic field and the fallout and deposition of cosmogenic beryllium at the surface happen on a very short time scale however investigations performed on terrestrial and marine successions demonstrate that the 10be record and the paleomagnetic signal are often asynchronous mechanisms that control the conveyance and deposition of cosmogenic 10be to the seafloor are still ambiguous and poorly documented here we discuss the dynamics of 10be in a central mediterranean marginal marine depositional scenario characterized by a pervasive terrigenous influx our data show that a very close correlation exists between 10be concentrations and the local proxy of rainfall rates and regimes pollen indicating that a considerable 10be transport from the mainland may occur in response to the remobilization of terrestrial reservoirs during periods of increased runoff superimposed is a dynamic oceanographic setting that further controls the preservation potential of 10be at the bottom in terms of changing water chemistry and or composition of the sedimentary flux to the seafloor results of our investigation suggest that in particular environmental and depositional settings the interplay between climate terrigenous yield and oceanography may jeopardize the sedimentary depiction of the meteoric 10be contribution thus challenging the use of 10be for tracking the stratigraphic position of geomagnetic reversals

abnormal carbonate diagenesis in holocene late pleistocene sapropel associated sediments from the eastern mediterranean evidence from emiliania huxleyi coccolith morphology in studying the holocene late pleistocene record of the eastern mediterranean considerable emiliania huxleyi size shape variation not clearly assignable to primary or secondary calcification was observed accordingly different morphotypes were distinguished by light microscope lm a subsequent scanning electron microscope sem analysis of selected samples has indicated that emiliania huxleyi coccoliths are variably affected by carbonate diagenesis in these sediments a series of diagenetic stages were qualitatively defined comprising well preserved specimens three overgrowth og1 to og3 and one etching e1 stage comparing sem and lm observations a tentative correlation between the e huxleyi calcified lm morphotypes and e huxleyi sem overgrowth stages is proposed here our study not only indicates that emiliania huxleyi coccoliths are strongly influenced by carbonate diagenesis but also that they show effects of carbonate precipitation and dissolution much more clearly than other coccoliths the relative abundances of the different lm morphotypes were used to define an e huxleyi overgrowth index exo that qualitatively estimates carbonate precipitation dissolution on coccoliths in this sediment this resulted in definition of five diagenetic intervals d1 to d5 deposition of sapropel s1 was a time of good preservation with variable dissolution and no overgrowth of e huxleyi coccoliths whereas calcite overgrowth was high during the last glacial maximum lgm and interglacial period and to a lesser extent during the younger dryas and through the last 5 ka d 2004 elsevier b v all rights reserved

selective aerobic and anaerobic degradation of lipids and palynomorphs in the eastern mediterranean since the onset of sapropel s1 deposition abstract selective degradation of organic matter in sediments is important for reconstructing past environments and understanding the carbon cycle here we report on compositional changes between and within lipid classes and kerogen types represented by palynomorph groups in relation to the organic matter flux to the sea floor and oxidation state of the sediments since the early holocene for central eastern mediterranean site abc26 this includes the initially oxic but nowadays anoxic presapropelic interval the still unoxidised lower part of the organic rich s1 sapropel its postdepositionally oxidised and nowadays organic poor upper part as well as the overlying postsapropelic sediments which have always been oxic a general 2 3 times increase in terrestrial and marine input during sapropel formation is estimated on the basis of the total organic carbon toc pollen spore dinoflagellate cyst n alkane n alkanol and n alkanoic acid concentration changes in the unoxidised part of the sapropel the long chain alkenones 1 15 diols and keto ols loliolides and sterols indicate that some plankton groups notably dinoflagellates may have increased much more apart from the terrestrial and surface water contributions to the sedimentary organic matter anomalous distributions and preservation of some c 23 c 27 alkanes alkanols and alkanoic acids have been observed which are interpreted as a contribution by organisms living in situ comparison of the unoxidised s1 sapropel with the overlying oxidised sapropel and the organic matter concentration profiles in the oxidised postsapropelic sediments demonstrates strong and highly selective aerobic degradation of lipids and palynomorphs there seems to be a fundamental difference in degradation kinetics between lipids and pollen which may be possibly related with the absence of sorptive preservation as a protective mechanism for palynomorph degradation the n alkanes impagidinium and nematosphaeropsis are clearly more resistant than toc the n alkanols and n carboxylic acids are about equally resistant whereas the pollen all other dinoflagellate cysts and other lipids appear to degrade considerably faster which questions the practice of normalising to toc without taking diagenesis into account selective degradation also modifies the relative distributions within lipid classes whereby the longer chain alkanes alcohols and fatty acids disappear faster than their shorter chain equivalents accordingly interpretation of lipid and palynomorph assemblages in terms of pre or syndepositional environmental change should be done carefully when proper knowledge of the postdepositional preservation history is absent two lipid based preservation proxies are tested the diol keto ol oxidation index based on the 1 15c 30 diol and keto ols doxi and the alcohol preservation index api whereby the former seems to be the most promising

pliocene holocene evolution of depositional conditions in the eastern mediterranean role of anoxia vs productivity at time of sapropel deposition a multiproxy geochemical study of nine sapropel layers from odp hole 964a odp leg 160 in the eastern mediterranean spanning the pliocene holocene time interval provides new insights into the evolution of sapropel deposition paleoenvironmental proxies were used for reconstruction of productivity ba derived from marine barite oxygen conditions trace metal ratios and sedimentary regime clay minerals detrital elements these proxies reveal a significant increase in river runoff relative to decreasing aeolian input during sapropel deposition over the whole time interval ba excess supports the argument that a significant increase in export productivity is the main triggering mechanism for sapropel deposition although preservation also played an important role furthermore major differences exist in depositional conditions including both oxygenation and productivity since the pliocene productivity fluctuated substantially and was higher during the pliocene and pleistocene than during the holocene at the same time decreasing oxygen availability parallels the enhanced productivity dysoxic to anoxic conditions appear to coincide with marine productivity maxima thus suggesting that oxygen depletion may be linked to greater consumption rather than restricted circulation this correspondence supports the hypothesis that productivity fluctuations resulting from climate oscillations were the main cause of enhanced organic matter contents and also a main controlling factor for reduced oxygen availability

a novel selective extraction of barite and its application to eastern mediterranean sediments abstract a sequential extraction method basex was developed to determine the different ba fractions in sediments calibration of basex with pure barite and a home made mixed mineral standard showed that barite is separated from all other major ba containing mineral phases such as clay minerals and fe and mn oxides this method permits the direct determination of sedimentary barite content and of the ba al ratio of clay and is therefore a useful tool in palaeoclimatic studies application of basex to eastern mediterranean sediments including sapropel s1 revealed that the enrichment in ba concentrations observed in this sapropel consists predominantly of barite the relationship of barite ba with organic carbon in sapropel s1 sediments appears to be independent of water depth of organic matter fluxes and of the sedimentation rate for cores ranging from 2150 to 3300 m water depth apparently organic carbon remineralisation has been virtually absent in the water column deeper than 2150 m this might have been caused by suboxic to anoxic conditions present in the deep eastern mediterranean basin during the formation of sapropel s1 because of the constant relationship between barite and organic carbon in sapropelic sediments we suggest that the barite content can be used to quantify the initial organic carbon content of the sediment in the oxidised sapropel interval