stratigraphy and strontium geochemistry of messinian evaporite bearing successions of the southern apennines foredeep italy implications for the mediterranean salinity crisis and regional palaeogeography an integrated study comprising detailed mapping stratigraphy evaporite facies analysis strontium content and 87sr 86sr ratio data is presented for two messinian evaporite bearing units cropping out in irpinia daunia mountains southern apennines italy these units record the tectonic and palaeogeographic evolution of the messinian southern apennine foreland basin system during the abrupt salinity crisis which occurred in the mediterranean region the daunia unit comprises the monte castello evaporites formed by euxinic diatomitic marls evaporitic limestones and shallow water gypsum having a 87sr 86sr average value of 0 70898 0 00005 close to the sr isotopic value of the coeval seawater these marginal evaporites are capped by an erosional unconformity and continental clastic deposits the vallone del toro unit is made up of thin bedded marls claystones calcilutites and diatomite layers with small gypsum crystals laminated gypsum and gypsarenite testifying deposition in relatively deep water settings gypsum has variable sr isotopic data with an average value of 0 70899 0 00005 for the argilliti policrome del torrente calaggio formation and an average value of 0 70863 0 00014 for the argilliti di mezzana di forte formation reflecting major riverine freshwater input the different patterns of lithofacies and sr isotopic composition of gypsum discriminate two distinctive evaporite units reflecting the tectonic and palaeogeographic controls within the apennines mountain belt and the mediterranean data for evaporites of the southern apennines testify the presence of basins in the central and eastern mediterranean sea which never desiccated during the entire salinity crisis and evolved to widespread lago mare conditions in the latest messinian

geochemical and mineralogical impacts of h2so4 on clays between ph 5 0 and 3 0 natural and constructed clay liners are routinely used to contain waste and wastewater the impact of acidic solutions on the geochemistry and mineralogy of clays has been widely investigated in relation to acid mine drainage systems at ph 1 0 the impact of h2so4 leachate characterized by ph 1 0 and potentially negative ph values on the geochemistry and mineralogy of clays is however not clear thus laboratory batch experiments were conducted on three natural clay samples with different mass ratios of smectite illite and kaolinite to investigate the impact of h2so4 on the geochemistry and mineralogy of aluminosilicates from ph 5 0 to 3 0 batch testing was conducted at seven ph treatments 5 0 3 0 1 0 0 0 1 0 2 0 and 3 0 using standardized h2so4 solutions for four exposure periods 14 90 180 and 365 d aqueous geochemical and xrd analyses showed increased dissolution of aluminosilicates with decreasing ph and increasing exposure period that smectite was more susceptible to dissolution than illite and kaolinite precipitation of an amorphous silica phase occurred at ph 0 0 and anhydrite precipitated in ca rich clays at ph 1 0 in addition global dissolution rates were calculated for the clays and showed good agreement to literature smectite illite and kaolinite dissolution rates which suggests global dissolution rates for complex clays could be determined from monomineralic studies a stepwise conceptual model of the impact of h2so4 on aluminosilicate geochemistry and mineralogy between ph 5 0 and 3 0 is proposed

tectonics and sequence stratigraphy in messinian basins sicily constraints on the initiation and termination of the mediterranean salinity crisis deposits within the caltanissetta basin of central sicily have been important for developing the desiccating deep basin model for the messinian salinity crisis in the mediterranean linked structural and stratigraphic studies show that the sicilian depocenters are synclines related to underlying thrust structures of the frontal part of the maghrebian chain prior to the salinity crisis these basins were hydrodynamically linked through the foredeep to the mediterranean the precursor sediments terravecchia formation formed a delta sourced from the north early messinian regression acted on a range of paleobathymetries shallow in the north and progressively deeper in the south locally complicated by active thrust structures initial draw down of mediterranean base level is marked across the thrust belt by first cycle carbonates and evaporites on the structural highs and lows respectively vast accumulations of halite and potassium salts up to 1200 m are restricted to growing thrust synclines the different evaporite signatures may be related to different water conditions reflecting various meteoric and marine circulations across various subbasins with cyclicity reflecting high frequency variations in sea level a sequence stratigraphic model is developed to explain fractionation of evaporite facies between different paleobathymetric settings and to predict the temporal evolution of the successions in different subbasins thrusting provides accommodation space for evaporites and also controls the water pathways into the desiccating basins the intra messinian unconformity separating first and second cycle evaporites is a type 1 sequence boundary related to the forced regression associated with the acme of mediterranean desiccation an interpretation supported by local ravinement and incised valley fills the overlying second cycle evaporites are a combination of detrital reworked first cycle material and primary gypsum formed under brackish water regional onlap relationships and bed continuity suggest that this water body was of regional extent with a systematically rising base level these interpretations have several implications for messinian correlations in the mediterranean the deep basin evaporites correlate with an intra messinian unconformity that separates the two cycles on sicily and postdate the first cycle deposits regional base level was largely restored before the end of the salinity crisis

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

tracing interactions between natural argillites and hyper alkaline fluids from engineered cement paste and concrete chemical and isotopic monitoring of a 15 years old deep disposal analogue abstract samples of toarcian argillite were collected both next to and far from a cem ii cement paste and a cem ii concrete within the specific context of a 15 a old borehole located in the tournemire experimental platform aveyron france the objectives were evaluation of the mineralogical and geochemical changes of the claystone at the contact with the cementitious materials and determination of the spatial extent of the interactions the approach includes the examination of the mineralogical xrd sem tem chemical major trace rare earth elements and isotopic sr c o compositions of argillite whole rocks and of various soluble phases at two scales in the rock matrix p1 scale and along micro cracks p2 scale the two study scales outline nearly similar mineralogical modifications shown by the presence of ca silicate hydrates c s h and newly formed caco 3 within 10 15 mm of the cement paste and concrete chemical data from whole rock argillites indicate few changes in a slightly thicker zone 18 20 mm mainly consisting of an increase in the cao wt and a decrease in sr contents the other elementary contents remained quite constant except for mgo which suggests redistribution with precipitation of a mg rich mineral phase at 20 mm from cement paste concrete interface acetic acid leachates had more pronounced variations including a decrease of the total elementary content in the same geochemical disturbed zone gdz together with a significant increase of the sr isotopic ratios a combination of sr and c o isotopic patterns was used to distinguish the behavior of secondary cementitious phases in the clay rich rock i calcite dissolution and re precipitation is supported by c o isotopic data and ii c s h neoformation is evidenced by the 87 sr 86 sr ratios this tool also contributes to determine the origin of the fluids the proportion of newly formed c s h in the matrix and in the micro cracks of the argillite is modeled

rock alteration in alkaline cement waters over 15 years and its relevance to the geological disposal of nuclear waste the interaction of groundwater with cement in a geological disposal facility gdf for intermediate level radioactive waste will produce a high ph leachate plume such a plume may alter the physical and chemical properties of the gdf host rock however the geochemical and mineralogical processes which may occur in such systems over timescales relevant for geological disposal remain unclear this study has extended the timescale for laboratory experiments and shown that after 15 years two distinct phases of reaction may occur during alteration of a dolomite rich rock at high ph in these experiments the dissolution of primary silicate minerals and the formation of secondary calcium silicate hydrate c s h phases containing varying amounts of aluminium and potassium c a k s h during the early stages of reaction up to 15 months have been superseded as the systems have evolved after 15 years significant dedolomitisation mgca co3 2 2oh mg oh 2 caco3 co32 aq has led to the formation of magnesium silicates such as saponite and talc containing variable amounts of aluminium and potassium mg al k silicates and calcite at the expense of the early formed c a k s h phases this occured in high ph solutions representative of two different periods of cement leachate evolution with little difference in the alteration processes in either a koh and naoh or a ca oh 2 dominated solution but a greater extent of alteration in the higher ph koh naoh leachate the high ph alteration of the rock over 15 years also increased the rock s sorption capacity for u vi the results of this study provide a detailed insight into the longer term reactions occurring during the interaction of cement leachate and dolomite rich rock in the geosphere these processes have the potential to impact on radionuclide transport from a geodisposal facility and are therefore important in underpinning any safety case for geological disposal

sedimentary stable isotope and micropaleontological records of paleoceanographic change in the messinian tripoli formation sicily italy abstract the tripoli formation 6 96 5 98 ma of the central sicilian basin provides a good record of the paleoceanographical changes that affected the mediterranean during the transition from slightly restricted conditions to the onset of the messinian salinity crisis the falconara gibliscemi section has been selected for an integrated approach at a high resolution scale using sedimentology stable isotopes of the carbonates and microfossils the sedimentary succession includes 46 precession controlled cycles resulting from the periodical increase in biosiliceous productivity diatomites that followed the deposition of marls and pinkish laminites which appear as sapropel type deposits induced by the oceanic fertilization by terrestrial nutrients during wet periods higher scale environmental changes are superimposed to this precession forced rhythmicity there is a general trend of increasing basin restriction from near marine conditions at the base of the tripoli to semi closed settings in its uppermost part which are the prelude of the salinity crisis this pattern reflects the hydrological response of the mediterranean to the progressive decrease of the atlantic inputs and an enhanced influence of the climate on depositional conditions however this evolution is not linear and shows successive phases of different duration during the first period until 6 71 ma open atlantic mediterranean exchanges maintained relatively stable marine conditions the second period 6 71 6 29 ma marks an important step in the basin restriction with a wider range of salinity fluctuations and an increased bottom stagnation the 6 71 ma event which is correlated at a mediterranean scale may have resulted from shallowing of the mediterranean gateway under a tectonic control this shallowing reduced the oceanic inputs resulting in an increased climatic constraint of the mediterranean hydrology during the third period 6 29 6 03 ma an increase of the surface water salinity resulted in stressful conditions for the marine microfauna the 6 29 ma change is a major step in the restriction that may be correlated with the intensification of the glaciation recorded in the atlantic which could have enhanced the effects of the tectonic closure the last two cycles 48 and 49 that underlie the calcare di base witnessed the rapid transition to a semi closed mediterranean setting characterized by large variations of salinity from diluted to hypersaline conditions under a dominant climatic control and by the nearly complete disappearance of the marine organisms long trend environmental changes recognized within the tripoli formation resulted from a complex set of interfering factors controlling the water fluxes exchanged between the mediterranean and the world ocean most of the rapid changes identified in falconara gibliscemi at 7 16 6 71 and 6 29 ma that occurred simultaneously in the western and eastern mediterranean were mainly controlled by the stepwise tectonic closure of the atlantic connections although a glacio eustatic overprint cannot be completely excluded

isotope geochemistry petrology and depositional environments of the diatomite dominated tripoli formation lower messinian sicily the tripoli formation lower messinian in sicily includes diatomites irregularly alternating with marl and carbonate beds and lies stratigraphically between the tortonian pelagic marls and the evaporitic calcare di base the relationships between mineralogy textural features and oxygen carbon isotopic compositions of carbonate components point to a wide variability of depositional conditions and suggest that tripoli sedimentation occurred in small basins characterized by periodic and marked restriction from the open sea the isotopic values of calcite and dolomite in the diatomites suggest an evolution from normal marine towards more restricted environments evaporating conditions are also indicated by the occurrence of anhydrite length slow chalcedonic quartz and moulds of gypsum in a more advanced stage the precipitation of heavy 180 dolomite in the interstitial pores of fossil poor diatomites denotes an environment with highly evaporated water mixing of meteoric and marine waters on the other hand might have favoured the precipitation of a dolomite characterized by relatively low 180 and 13c values the deposition of marl and carbonate beds alternating with or overlying the diatomites took place in an environment with highly evaporated marine waters on the basis of l18o values of dolomite up to 9 10 and aragonite up to 5 83 occurrence of evaporitic minerals and lack of fossils the presence at these levels of calcite with extremely negative 13c values down to 38 40 filling gypsum moulds suggests activity of sulphate reducing bacteria some aragonitic marls however bear evidence of deposition in relatively normal marine conditions

stable isotope mapping in messinian evaporative carbonates of central sicily mapping stable isotope isolines in both modern and ancient evaporative carbonate formations demonstrates that regional variations of 18 o values exist in the case of the messinian central sicilian basin an ancient evaporite basin the distribution pattern of the 18 o isolines can be related to the paleogeometry and paleohydrology of the basin isolines of equal 13 c values also show large regional variations possibly reflecting the domination of different bacterial processes oxidation sulfate reduction or methanogenesis in different regions the potential application for stable isotope mapping in evaporative carbonate formations deposited in both marine and lacustrine environments lies in its ability to predict the location of depositional centers in ancient evaporite basins

the messinian calcare di base sicily italy revisited three different types of carbonate deposits are included within the calcare di base commonly envisaged to record the messinian salinity crisis onset type 1 consists of sulfur bearing limestones representing the biogenic product of bacterial sulfate reduction after original gypsum type 2 comprises dm thick laminated dolomitic limestones interbedded with diatomites sapropels and marls found at the top the tripoli formation type 3 the most common variety consists of m thick brecciated limestones interbedded with shales and clastic gypsum type 3 shows sedimentary features suggesting a clastic origin and deposition from high to low density gravity flows thus these deposits can be regarded as an end member of a large variety of evaporite bearing gravity flow deposits with a dominant carbonate component the genetic and stratigraphic characterization of these carbonates has strong implications for a better comprehension of messinian events the three types of calcare di base seem to have formed during different stages of the messinian salinity crisis msc type 2 formed in the first stage 5 96 5 60 ma and is the only type that can be regarded as the lower gypsum time equivalent type 3 was deposited in the second stage 5 60 5 55 ma and its base is associated with a regional scale hiatus and erosion messinian erosional surface type 1 formed even later likely in post messinian time through diagenetic processes affecting resedimented gypsum deposited during the second stage of the msc it follows that not all the calcare di base deposits record the onset of the messinian salinity crisis as commonly thought thus a detailed facies characterization of these carbonate deposits is fundamental for both stratigraphic reconstructions and a better comprehension of messinian events

semi automatic determination of the carbon and oxygen stable isotope compositions of calcite and dolomite in natural mixtures a semi automatic on line method was developed to determine the delta 13 c and delta 18 o values of coexisting calcite and dolomite an isotopic mass balance is used to calculate the compositions of dolomite after having measured that of calcite and of the bulk sample the limit of validity of this method is established by performing isotopic measurements of artificial mixtures made of precisely weighted and isotopically characterised dolomite and calcite the accuracy and repeatability of the calculation of dolomite delta 13 c and delta 18 o are statistically determined with a monte carlo procedure of error propagation stable isotope ratios are determined by using an automated multiprep t system on line with an isotope ratio massspectrometer irms the reaction time and the temperature of reaction were optimised by comparing the results with the isotopic composition of known mixtures the best results were obtained by phosphoric acid digestion after 20 min at 40 degrees c for calcite and 45 min at 90 degrees c for dolomite this procedure allows an accurate determination of the isotopic ratios from small samples 300 mu g application of this protocol to natural mixtures of calcite and dolomite requires the accurate determination of the relative abundance of calcite and dolomite by combining melieres manocalcimetry mmc and x ray diffractometry xrd

carbonate preservation and climatic changes in the central red sea during the last 380 kyr as recorded by pteropods abstract numerical abundances of pteropods and planktic foraminifera and the mode of pteropod preservation were determined in core kl 11 taken from the central part of the red sea the abundance of pteropods shells g dry sediment was compared to that of planktic foraminifera pt pf pt a technique that permits detection of changes in carbonate preservation for the last 380 kyr the numerical abundance of pteropods is influenced by the properties of the water column and preservation is influenced by the bottom water during the last 200 kyr except during isotope stage 5 5 carbonates are in general well preserved during this period the abundance pattern of the pteropods and planktic foraminifera is very similar and follows the climatic signal of the red sea with high numbers during the interglacial stages changing to very low numbers during glacial maximum conditions the similar abundance trends of the two groups and between them and the 18o curve indicates abundance is strongly linked to salinity from isotope stage 6 to the bottom of the core the pteropods occur in low numbers unlike the planktic foraminifera which continue to display the high amplitude glacial interglacial cyclicity the deviations mainly during interglacial stages between the abundance pattern of the two groups and the low pt pf pt values indicate a significant change in carbonate preservation distinctive carbonate dissolution intervals are recognized in the red sea correlating to large scale deep water dissolution events of the mid brunhes dissolution cycle in the indian ocean the anti estuarine circulation pattern of the red sea prevents a direct connection between the deep water masses of the two oceans and rules out the likelihood that changes in the deep water circulation caused these carbonate dissolution events the numerical variations between nonmigratory epipelagic and migratory mesopelagic pteropods were used to evaluate changes in the structure of the water column abundance maxima of mesopelagic pteropods as in the recent red sea indicate an aerated water column with 0 5 ml o2 l oxygen concentrations at the minimum zone mesopelagic abundance maxima coincide commonly with negative monsoonal index values indicating a more aerated water column connected to increasing aridity in the red sea region abundance maxima of epipelagic pteropods indicate a strongly stratified water column at times causing severe depletion in oxygen at intermediate water depths epipelagic peak events coincide often with positive monsoon index values implying an overall milder and more humid climate in the red sea probably associated with enhanced precessional controlled southwest monsoon activity

the origin of fluoride rich groundwater in mizunami area japan mineralogy and geochemistry implications abstract the aim of this paper was to explore new factors that might be reasons for the occurrence of fluoride rich groundwater in the area around a construction site during the construction of two deep shafts of the mizunami underground research laboratory miu in mizunami city central japan a large quantity of groundwater with high fluoride concentration was charged into the shafts chemical investigation carried out during the excavation revealed that fluoride concentrations in the area around the miu site greatly exceeded those prescribed by japanese standards therefore the origin of fluoride ion was experimentally investigated samples were collected from the core of a deep borehole drilled in the study area the weathering and alteration levels of the collected granites varied greatly granitic powders were used to measure fluoride content in the granitic rock mass the fluoride content ranged between 200 and 1300 mg kg the powders were reacted with purified water for 80 days the results of water rock interaction showed granitic rock to be one of the main sources of fluoride rich groundwater in mizunami area fluoride concentrations in these solutions that were shaken for 80 days varied between 2 and 7 mg l this change may have occurred as a result of the spatial distribution of fluoride ions in the granite mass as evidenced by mineralogical analysis of fluoride content in several specimens x ray powder diffraction analysis of the rock before and after the water rock interaction tests manifested that the presence of fluorite mineral was relatively small compared to other minerals the degree of weathering and alteration might be an additional factor causing dissolution of fluoride rich minerals however it was difficult to interpret the change in fluorite composition by x ray diffraction analysis

extending the astronomical polarity time scale into the miocene an astronomical time scale is presented for the late miocene based on the correlation of characteristic sedimentary cycle patterns in marine sections in the mediterranean to the 65 n summer insolation curve of la90 1 2 with present day values for the dynamical ellipticity of the earth and tidd dissipation by the moon this correlation yields ages for all sedimentary cycles and hence also for the recorded polarity reversals and planktonic foraminiferal and dinoflagellate events the tortonian messinian t m boundary placed at the first regular occurrence of the globorofuliu conomiozea group in the mediterranean is dated at 7 24 ma the duration of the messinian is estimated at 1 91 myr because the miocene pliocene boundary has been dated previously at 5 33 ma 3 the new time scale is confirmed by oar 3gar ages of volcanic beds and by the number of sedimentary cycles in the younger part of the mediterranean messinian

a new method for quantitative petrography based on image processing of chemical element maps part ii semi quantitative porosity maps superimposed on mineral maps visualizing and quantifying the spatial heterogeneity of rock textures i e mineral and porosity distributions is of great interest in petrology or for understanding petrophysical properties spatial heterogeneities are not accurately revealed by usual techniques based on microscopy or bulk physical measurements detailed mineral mapping is already available from processing of chemical element maps acquired using an electron probe microanalyzer part i the present paper is devoted to developing a new coupled method for obtaining porosity maps from the same initial data according to the difference between measured and theoretical sums of oxide weight percentages a mean porosity is semi quantitatively estimated for each pixel of the map i e not fully absolute or accurate all pores including nanometer size ones are taken into account whereas a sample area of several square millimeters is analyzed spatial resolution of a few micrometers the textural heterogeneities are thus visualized from the complementary maps of solids and voids by superimposing these two maps both the mean porosity and a porosity histogram associated with each rock forming mineral are obtained such porosity measurements integrate the pore amounts within mono crystals larger than the x ray emission volume or between nanometer size crystals of a matrix when porosity changes are associated with a given mineral various crystal arrangements dissolution etc pluri modal distributions appear on porosity histograms thresholding each histogram mode then allows these processes to be localized we used the mx80 bentonite to test this methodology which represents a useful tool to study the local deformations and alteration of each rock forming mineral as well as to model transport properties

late pliocene to early pleistocene astronomically forced sea surface productivity and temperature variations in the mediterranean abstract principal component analysis of late pliocene to early pleistocene planktonic foraminiferal abundances from the mediterranean yielded two significant components which represent first order approximations for sea surface productivity and temperature this interpretation is confirmed by the good fit between the score plots and sea surface productivity and sea surface temperature proxy records based on selected eutrophic and temperature sensitive species using present day habitat characteristics spectral analysis revealed significant peaks in the orbital frequency bands of the spectrum suggesting that variations in sea surface productivity and temperature are controlled by the quasi periodic variations in the earth s orbit precession forced variations are reflected primarily in sea surface productivity and to a lesser degree in sea surface temperature maxima in sea surface productivity and temperature in this frequency band occurred at times of sapropel formation the sea surface productivity maxima can be explained by an increased input of river borne nutrients and by the shoaling of the pycnocline and the associated intensification of the deep chlorophyll maximum dcm layer precession forced variations in sea surface temperature are not related to glacial cycles since this frequency component is almost completely absent in ice volume proxy records for this time interval sapropel bound sea surface temperature maxima presumably reflect periods of maximum insolation during the northern hemisphere summer the contrasting winter signal corresponds to minimum insolation values which may be reflected by peak abundances ofgloborotalia inflata obliquity forced variations are reflected primarily in sea surface temperature and not in sea surface productivity these temperature fluctuations correspond with ice volume changes registered in the oxygen isotope record at the north atlantic dsdp site 607 this shows that obliquity forced sea surface temperature variations in the mediterranean are primarily driven by glacial cycles

decoding the mediterranean salinity crisis this historical narrative traces the steps to unravel over a span of 40 years an extraordinary event in which 5 of the dissolved salt of the oceans of the world was extracted in a fraction of a million years to form a deposit more than 1 million km 3 in volume a buried abyssal salt layer was identified with reflection profiling and sampled during the deep sea drilling project leg 13 the dolomite gypsum anhydrite and halite in the drill cores paint a surprising picture of a mediterranean desert lying more than 3 km below the atlantic ocean with brine pools that shrank and expanded by the evaporative power of the sun the desert drowned suddenly when the gibraltar barrier gave way the explanation of deep basin shallow water desiccation and the notion of a catastrophic zanclean flood had a mixed reception however the hypothesis became broadly accepted following subsequent drilling expeditions nevertheless as experts examined the evaporate facies and sequences of equivalent age in the terrestrial outcrops weaknesses appeared in the concept of repeated flooding and drying to account for the magnitude of the deposits the rosetta stone used to decipher conflicting interpretations turns out not to be the deposits but the erosion surfaces that enclose them these surfaces and their detritus formed in response to the drop in base level during evaporative drawdown extend to the basin floor evaporative drawdown began halfway through the salinity crisis when influx from the atlantic no longer kept up with evaporation prior to that time a million years passed as a sea of brine concentrated towards halite precipitation during the later part of this interval more than 14 cyclic beds of gypsum accumulated along shallow margins modulated by orbital forcing the thick salt on the deep seabed precipitated in just the next few cycles when drawdown commenced and the brine volume shrank upon closure of the atlantic spillway the remnants of the briny sea transformed into salt pans and endorheic lakes fed from watersheds of eurasia and africa the revised model of evaporative concentration now has shallow margin shallow water and deep basin deep water precursors to desiccation

a shallow water record of the onset of the messinian salinity crisis in the adriatic foredeep legnagnone section northern apennines abstract the legnagnone section north eastern apennines represents one of the few shallow water records of the onset of the messinian salinity crisis here we present a detailed description of a 200 kyr time interval encompassing the pre syn evaporitic transition based on a multidisciplinary approach integrating sedimentological bio magnetostratigraphical palaeontological and stable isotope data such a shallow water setting is potentially more sensitive to the palaeoenvironmental change leading to the msc than the more often studied deeper mediterranean basin the aquatic palaeoenvironmental reconstruction proposed here is based on the study of foraminifer ostracod and mollusc assemblages it depicts a change from infralittoral 20 50 m to inner circalittoral environment 60 100 m that since 6 12 ma was progressively affected by a reduction of oxygen at the sea floor punctuated by short lived anoxic events at least three cooling events have been recognized on the basis of relative abundance data in mid to high altitude pollen which before 6 03 ma are in phase with abundance peaks of turborotalia spp a taxon indicating eutrophic and cool surface waters the absence of stress tolerant benthic foraminifers during these peaks points to strong ventilation episodes triggered by a generally cooler climate the proximity of a deltaic system and the consequent riverine input probably caused a salinity decrease of the surface waters hindering the proliferation of planktonic foraminifers in the water column which prevalently occur in short influxes and disappear at ca 6 ma our results suggest that the onset of the crisis occurred during a phase of relative sea level high stand whereas no evidences of sea level drop can be envisaged the palaeoclimatic reconstruction based on palynological data indicates the dominance of a subtropical humid forest vegetation type where fresh water swamps are well represented from 6 03 ma onward the transition to the salinity crisis is marked by more pronounced cyclical expansions of the temperate broad leaved deciduous forest along with herbaceous taxa the establishment of the strongly evaporative condition at the crisis onset is not associated with major vegetational changes towards drier conditions but linked to a sudden increase of 18o and the disappearance of benthic foraminifers just prior to the deposition of the 1st laminated carbonate which represents the base of the primary lower gypsum unit

messinian carbonate rich beds of the tertiary piedmont basin nw italy microbially mediated products straddling the onset of the salinity crisis abstract the seven messinian microbial carbonate rich layers cropping out in the pollenzo section tertiary piedmont basin nw italy are interbedded with a precession related cyclic succession composed of euxinic shale marl couplets and straddle the onset of the messinian salinity crisis msc a sharp change of sedimentological compositional and geochemical characteristics was observed from the onset of the msc onward suggesting strong differences in the mechanisms responsible for carbonate precipitation pre msc beds are mainly composed of dolomite and are interpreted as the product of early diagenesis formed by bacterial sulphate reduction in the shallow subsurface along the sulphate methane interface dolomite precipitation was temporarily enhanced by an upward flux of methane rich fluids possibly sourced by gas hydrate destabilisation conversely from the onset of the msc onward carbonate beds are thinly laminated and show abundant filaments interpreted as beggiatoa like bacteria while calcite and aragonite are the dominant authigenic phases these beds are interpreted as microbialites resulting from the lithification of chemotrophic bacterial mats dominated by sulphide oxidizing bacteria the carbonate necessary for their preservation was provided by bacterial sulphate reduction these microbialites that appear as the deeper water counterpart of bottom grown selenite layers deposited in the marginal part of the basin formed on an anoxic sea bottom under a density stratified water column the high sulphate concentration in the pore waters related to the presence of concentrated brines and to the regeneration of sulphate by sulphide oxidizing bacteria is considered as the driving factor controlling the mineralogical change from dolomite to calcite and aragonite finally the sharp shift towards negative 18 o values of carbonates observed from the onset of the msc onward was probably related to fractionation processes operated by sulphate reducing bacterial communities in the pore waters this suggests that care must be taken when dealing with microbial carbonates in the interpretation of the oxygen isotope values in terms of fluctuating salinity condition of the water mass in conclusion this study suggests that the onset of the msc had a strong impact on microbial populations governing carbonate precipitation in a sector of the basin dominated by depositional conditions not suitable for gypsum precipitation

vegetation sea level and climate changes during the messinian salinity crisis the messinian salinity crisis late miocene is one of the most fascinating paleoceanographic events in the recent geological history of the mediterranean sea defining a time when it partly or nearly completely dried out however the relative roles of tectonic processes and sea level changes as triggers for restriction and isolation of the mediterranean sea from the open ocean are still under debate in this study we present a detailed pollen dinoflagellate cyst dinocyst and magnetic susceptibility analysis of a sequence of late neogene between ca 7 3 and 5 2 ma marine sediments from the montemayor 1 core lower guadalquivir basin southwestern spain which provides a continuous record of paleoenvironmental variations in the atlantic side of the betic corridors during the late miocene our results show that significant paired vegetation and sea level changes occurred during the messinian likely triggered by orbital scale climate change important cooling events and corresponding glacio eustatic sea level drops are observed in this study at ca 5 95 and 5 75 ma coinciding with the timing and duration of oxygen isotopic events tg32 and tg22 20 recorded in marine sediments worldwide it is generally accepted that the onset of the messinian salinity crisis began at ca 5 96 0 02 ma therefore this study suggests that the restriction of the mediterranean could have been triggered at least in part by a strong glacio eustatic sea level drop linked to a climate cooling event occurring at the time of initiation of the messinian salinity crisis

messinian pre evaporite sapropels and precession induced oscillations in western mediterranean climate abstract cyclical fluctuations in planktic foraminiferal assemblages have been recognized in the pre evaporitic messinian in a marginal basin of the western mediterranean the fluctuations coincide with a dominantly precession controlled sedimentary cyclicity sapropels during sapropel deposition high planktic foraminiferal diversities are indicative of relatively stable marine conditions while during homogeneous marl deposition low diversities seem to indicate the presence of unfavourable more saline surface water conditions the dominance of a precession related signal indicates that regional climate oscillations rather than obliquity related glacio eustatically controlled influxes of atlantic and or mediterranean waters are responsible for the faunal fluctuations and sedimentary cyclicity our scenario links the persistence of normal marine conditions during sapropel formation with increased rainfall and run off along the western mediterranean at times that perihelion occurred in northern hemisphere summer less favourable highly saline surface water conditions prevailed during periods of drier climate induced by opposite precessional extremes the cyclical oceanographic fluctuations could also have governed periodic reef growth along the margins

lower devonian tentaculite bed in the satun area southern peninsular thailand a lower devonian emsian tentaculite fauna including nowakia acuaria richer r 1854 thuringische tentaculiten zeitschr deutsch geol gesellsch 6 275 290 occurs in black shale in the basal part of a siliciclastic sequence exposed north of satun southern peninsular thailand similar tentaculite beds with nowakia have been reported from several areas in the fang sri sawat and trang areas of thailand the langkawi islands and the mahang baling areas of malaysia the depositional environments in which the tentaculite bearing black shale accumulated extended from modern northern thailand to northwestern malaysia during the early devonian emsian

controls on faunal and sediment cyclicity within the tripoli and calcare di base basins late miocene of central sicily abstract cyclicity within the late miocene tripoli and calcare di base formations of sicily was controlled by two processes a partial evaporation of palaeomediterranean waters but with periodic replenishment by atlantic derived inflow on several occasions during the late tortonian and messinian stages b deformation of a regional foreland basin and associated satellite basins perched above south verging sedimentary thrust sheets these were intermittently set in motion by active plate collision onto the passive african plate margin although it is not possible to discriminate fully the world eustatic signal under such a scenario nevertheless sufficient recolonization by marine faunas in these sicilian basins occurred to permit modelling of onlap offlap events for the late miocene intervals basin wide correlation of these variably fossiliferous formations hangs on the recognition of a late tortonian early messinian onlap event marked by coral reef development at the top of the terravecchia formation around the northern margins of the region a further carbonate episode calcare di base formation lies above a transgressive surface and directly overlies fluvial conglomerates at the top of the terravecchia formation around the northern margins of the basin the calcare di base is partly diachronous with the top of the tripoli formation in the foreland basin but further north it oversteps the coral reefs on the southern margins of the madonie mountains a variable number of internal tripoli formation cycles confirmed on both faunal and sedimentological grounds and calcare di base cycles demonstrated only by sedimentation patterns have been recognized this minor cyclicity is considered to have resulted from periodic tectonic uplift and isolation of foreland basin and associated perched basins this isolation controlled both influx of siliciclastic sediment and access by marine biota prolonged basin isolation during the deposition of the tripoli formation lead to rapidly declining diversity patterns in both benthonic and planktonic communities benthonic foraminifera disappeared early in many cycles with oligotypic planktonic foraminifera and radiolaria remaining longest under increasingly hostile conditions only diatoms remained each new cycle is marked at its base by a return to near normal conditions and a relatively diverse biota although faunas were stressed during the isolation events no clear evidence of salinity increase is seen rather we consider that a combination of oxygen depletion especially on basin floors receiving prolific algal bioproduction and toxin build up generally as the by product of algal metabolic processes was the cause the calcare di base cycles are more difficult to interpret on account of the virtual absence of biota here the cycles are clearly related to desiccation and salinity increase during times of restriction the base of each cycle is marked by brine dilution and basin flooding with some evidence of low diversity microfauna input in the early cycles we envisage a late miocene palaeogeography with thrust fold belts well established to the north of sicily and a ne sw oriented seaway developed ahead of them to the south of this seaway lay an en echelon belt of ne sw oriented submarine ridges and localised basins which effected a sill or at times a barrier between the seaway and the tripoli basins a broad diatom dominated perched basin complex extended along the southern margin of the thrust related ridges and was intimately linked to a broad foreland basin also diatomitic lying immediately to the south the foreland basin was separated from a further open sea area in southern sicily by a second ne sw oriented sill now hidden by later overthrusting it is suggested that similar tectonic scenarios were responsible for isolating diatomaceous basin elsewhere in the mediterranean during late miocene times

surface expression of eastern mediterranean slab dynamics neogene topographic and structural evolution of the southwest margin of the central anatolian plateau turkey 1 the southwest margin of the central anatolian plateau has experienced multiple phases of topographic growth including the formation of localized highs prior to the late miocene that were later affected by wholesale uplift of the plateau margin our new biostratigraphic data limit the age of uplifted marine sediments at the southwest plateau margin at 1 5 km elevation to 7 17 ma and regional lithostratigraphic correlations imply that the age is 6 7 ma single grain ca tims u pb zircon analyses from a reworked ash within the marine sediments yield dates as young as 10 6 ma indicating a maximum age that is consistent with the biostratigraphy our structural measurements within the uplifted region and fault inversion modeling agree with previous findings in surrounding regions with early contraction followed by strike slip and extensional deformation during uplift focal mechanisms from shallow earthquakes show that the extensional phase has continued to the present broad similarities in the change in the tectonic stress regime after 8 ma and the onset of surface uplift after 7 ma imply that deep seated process es caused post 7 ma uplift the geometry of lithospheric slabs beneath the plateau margin pliocene to recent alkaline volcanism and the uplift pattern with accompanying normal faulting point toward slab tearing and localized heating at the base of the lithosphere as a probable mechanism for post 7 ma uplift of the southwest margin considering previous work in the region there appears to be an important link between slab dynamics and surface uplift throughout the anatolian plateau s southern margin

late miocene magnetostratigraphy biostratigraphy and cyclostratigraphy in the mediterranean a new chronology for the late miocene of the mediterranean is presented by combining magnetostratigraphic biostratigraphic planktonic foraminifera and dinoflagellates and cyclo stratigraphic data long and continuous upper miocene sections on gavdos metochia section and sicily gibliscemi section display cyclic alternations of homogeneous marls and sapropels and can be correlated on the basis of their distinct cyclic patterns the metochia section yields a good paleomagnetic signal and the position of 17 polarity reversals can be determined the resulting polarity sequence allows an unambiguous correlation to the geomagnetic polarity time scale gpts the paleomagnetic signal in the gibliscemi section is too weak to determine a reliable polarity sequence except for the lowermost part of the section detailed biostratigraphic analysis results in the identification of 13 planktonic foraminiferal and 9 dinoflagellate bioevents which can all be accurately dated the tortonian messinian boundary defined by the first regular occurrence fro of the g conomiozea group is determined in chron c3br 1r with an age of 7 12 ma according to the gpts ck95 of cande and kent 1

isotope stratigraphy 87sr 86sr δ18o δ13c of the sorbas basin betic cordillera spain paleoceanographic evolution across the onset of the messinian salinity crisis abstract the sorbas basin is a reference sector of the mediterranean basin for the definition of the onset of the messinian salinity crisis straddling the transition from the open marine deposits abad marls to the primary lower gypsum yesares formation during the first stage of the crisis between 5 97 and 5 60 ma because of its proximity to the atlantic gateway the sorbas basin is pivotal for the study of the oceanographic evolution that led to the most dramatic environmental event in the mediterranean sea we measured the carbon 13 c oxygen 18 o and strontium 87 sr 86 sr isotope ratio of 50 samples of planktonic foraminifera mollusk shells gypsum and carbonate sediments from the abad and yesares members turre and canos formation in the perales hueli los yesos and rio de aguas sections our results show a long term trend with most of the values plotting within the range of the global ocean strontium isotope curve and distinct short term fluctuations on precessional time scale the investigated geochemical proxies suggest that these oscillations reflect significant input of continental waters into the basin during the humid phase of a single precessional cycle this implies that the western mediterranean did not experience a main disconnection from the global ocean water before and during the first stage of the messinian salinity crisis and that different milankovitch forcings played a significant role in determining the seawater geochemistry

the deep water counterpart of the messinian lower evaporites in the apennine foredeep the fanantello section northern apennines italy abstract a possible deep water non evaporitic unit equivalent of the messinian lower evaporites has been recognised in the northern apennine foredeep this unit whose existence is implicitly admitted in the two step model of the mediterranean messinian salinity crisis is documented here for the first time it occurs throughout the apennine foredeep basin below a thick horizon of resedimented gypsum deposits usually ascribed to the lower evaporites actually the lower evaporites of the apennine foredeep basin include both shallow water in situ precipitated facies and deep water resedimented facies deposited in distinct depocenters the usually envisaged coeval nature of the two deposits has been recently challenged in several works based on a physical stratigraphic considerations about the downbasin correlation of the messinian erosional surface cutting on top the in situ evaporites with the sharp base of the resedimented evaporites unit and b the common occurrence of a barren unit below the resedimented evaporites which has no obvious equivalents in pre evaporitic successions underlying the in situ precipitated evaporites in this work a multidisciplinary study has been carried out on a 140 m thick composite section fanantello section to definitely assess the age and palaeoenvironmental characteristics of the unit underlying the resedimented gypsum deposits the topmost part of the section comprises a 60 m thick succession of barren euxinic shales falling entirely within a reversed polarity chron and characterised by a the complete disappearance of foraminifera b the occurrence of high salinity tolerant thecosomatous pteropods creseis sp c the abundance peaks of the calcareous nannofossil sphenolithus abies interpreted as related to highly stressed likely hyperhaline conditions d the appearance of hyperhaline and or stratified water molecular indicators gammacerane based on a multidisciplinary integrated stratigraphic approach this barren interval is here proposed to be a deeper water time equivalent of the in situ primary lower evaporites thus allowing to assess the events connected to the onset and the first phase of the messinian salinity crisis from a basinal perspective these data lend support to the hypothesis that the resedimented evaporite deposits of the apennine foredeep basin postdate the in situ evaporites thus implying that the term lower evaporites actually comprises rock bodies with different origins and separated in time and space by the messinian erosional surface and its correlative conformity this could be true also for other mediterranean basins where the stratigraphy of deep water successions should be carefully re examined

identifying late miocene episodes of connection and isolation in the mediterranean paratethyan realm using sr isotopes abstract after decades of research the timing and nature of late miocene connections between the mediterranean paratethys and the global ocean are still speculative the hydrologic flux implications of exchange or isolation are central to all hypotheses for generating the major lithological changes that represent the messinian salinity crisis moreover differences in the hydrologic fluxes envisaged are the primary distinction between models despite this these fluxes remain largely unconstrained this paper describes the basis for using sr isotope data innovatively combined with salinity data through hydrologic budget modelling to determine the timing and nature of mediterranean hydrologic connectivity we examine the hypotheses for three late miocene events to illustrate how this approach allows us to test implied hydrologic scenarios and exclude incompatible models 1 pre evaporite restriction of the mediterranean 2 the initiation of salt precipitation 3 connection between the sea of marmara and both paratethys and the mediterranean during the messinian this process suggests that the atlantic mediterranean exchange was significantly reduced up to three million years before evaporite precipitation it also indicates that end member hypotheses for initiating salt precipitation in the mediterranean desiccation and connected basin models are inconsistent with sr isotope data a contrasting model where evaporite formation was triggered by atlantic transgression into a strongly evaporation dominated mediterranean is shown to be more compatible with available datasets the application to sea of marmara samples indicates that salinity changes in the basin were not caused by changes to the amount of inflow from either paratethys or the mediterranean other possible as yet untested applications important for constraining different aspects of the messinian salinity crisis are highlighted

the effect of high ph alkaline solutions on the mineral stability of the boom clay batch experiments at 60 c abstract boom clay is currently viewed as a reference host formation for studies on deep geological disposal of radioactive waste in belgium the interactions between bulk rock boom clay and 0 1 m koh 0 1 m naoh 0 1 m ca oh 2 young cement water and evolved cement water solutions ranging in ph from 12 5 to 13 2 were examined as static batch experiments at 60 c to simulate alkaline plume perturbations which are expected to occur in the repository due to the presence of concrete both liquids and solids were investigated at specific times between 90 and 510 days in order to control the elemental budget and to search for potential mineralogical alterations also the clay fraction was separated from the whole rock boom clay at the end of each run and characterized for its mineralogical composition thereby the importance of the mineral matrix to buffer the alkaline attack and the role of organic matter to protect clay minerals were also addressed the results indicate that the degree of geochemical perturbation in boom clay is dependent on the initial ph of the applied solution together with the nature of the major cation in the reactant fluids the higher the initial ph of the media the stronger its interaction with boom clay no major non clay mineralogical alteration of the boom clay was detected but dissolution of kaolinite smectite and illite occurred within the studied experimental conditions the dissolution of clays is accompanied by the decrease in the layer charge followed by a decrease in the cation exchange capacity the highest toc values coincide with the highest total elemental concentrations in the leachates and correspondingly the highest dissolution degree however no quantitative link could be established between the degree of organic matter decomposition and clay dissolution

middle miocene pliocene stable isotope stratigraphy and paleoceanography of the mediterranean abstract stable isotope analyses of the planktonic foraminifers globigerinoides obliquus and globigerinoides trilobus from a number of sections from sicily italy yielded a rather detailed middle miocene to upper pliocene record a comparison between this record and previously published stable isotope records from the pacific and atlantic oceans suggests that at least during the time span considered the mediterranean had a paleoclimatic and paleoceanographic history that bears a close resemblance to that of the world s oceans four different local mediterranean overprints on the general isotope signal are distinguished 1 the disruption of the tethys sea way and the subsequent installation of a strong salinity stratification 2 short term eustatic sea level changes during the miocene resulting in salinity stratification and sapropel deposition 3 periodic increase of run off and subsequent salinity stratification during the pliocene also resulting in sapropel deposition 4 pliocene trends in the carbon isotope pattern deviating from the oceanic one the reason for which remained obscure

evolution of the late miocene mediterranean atlantic gateways and their impact on regional and global environmental change marine gateways play a critical role in the exchange of water heat salt and nutrients between oceans and seas as a result changes in gateway geometry can significantly alter both the pattern of global ocean circulation and associated heat transport and climate as well as having a profound impact on local environmental conditions mediterranean atlantic marine corridors that pre date the modern gibraltar strait closed during the late miocene and are now exposed on land in northern morocco and southern spain the restriction and closure of these miocene connections resulted in extreme salinity fluctuations in the mediterranean leading to the precipitation of thick evaporites this event is known as the messinian salinity crisis msc the evolution and closure of the mediterranean atlantic gateways are a critical control on the msc but at present the location geometry and age of these gateways are still highly controversial as is the impact of changing mediterranean outflow on northern hemisphere circulation here we present a comprehensive overview of the evolution of the late miocene gateways and the nature of mediterranean atlantic exchange as deduced from published studies focussed both on the sediments preserved within the fossil corridors and inferences that can be derived from data in the adjacent basins we also consider the possible impact of evolving exchange on both the mediterranean and global climate and highlight the main enduring challenges for reconstructing past mediterranean atlantic exchange

the monte carrubba formation messinian sicily and its correlatives new light on basin wide processes controlling sediment and biota distributions during the palaeomediterranean mediterranean transition abstract a little known marine miocene messinian succession in the hyblean region of south eastern sicily preserves a carbonate ramp sequence which developed on the tectonically stable foreland margins of the african plate pelagian block the ramp monte carrubba formation was distally steepened and contained a shoalwater barrier and lagoonal inner ramp complex the outer ramp is poorly preserved though distal deep water ramp facies tellaro formation in the south hyblean region preserve a full globorotalia mediterranea subzone and major part of the globigerina multiloba subzone succession this ramp sequence faithfully records the subtle interplay between the global eustatic curve and internal palaeomediterranean base level signatures for the late miocene the earliest second order palaeomediterranean lowstand occurred in the late tortonian at about 7 3 ma and a second occurred at about 6 75 ma within the early messinian g mediterranea subzone both were in the order of 40 m and global sea level was probably restored to the palaeomediterranean after the lowstands although the overriding control at the time was the global eustatic curve harmonic discrepencies between it and the palaeomediterranean curve resulted from constriction of the atlantic connection during the latest tortonian from about 6 4 ma until about 5 96 ma increasingly restricted conditions developed across the monte carrubba inner ramp these faithfully reflect many second order constriction driven palaeomediterranean sea level oscillations which were superimposed on to the falling global signal as the connecting atlantic seaways became constricted these oscillations resulted in major reductions in planktonic faunal diversity within the outer ramp followed by total emergence of the inner ramp by about 6 05 ma marine deposition continued until about 5 96 ma in the southern part of the hyblean region however between 6 05 ma and about 5 6 ma the amplitude of successive palaeomediterranean sea level oscillations increased to over 100 m causing prolonged periods of total palaeomediterranean isolation the hyblean carbonate suite also contains post messinian salinity crisis post msc lago mare highstand deposits which are developed unconformably above the monte carrubba formation the widespread distribution of hyposaline to near marine congeria faunas within the lago mare episode argues for high post msc mediterranean water levels in the central mediterranean late messinian in this article we draw together disparate regional evidence from this stable foreland setting and assimilate it with published data from regions lying on the european plate in order to demonstrate that the tectonically stable monte carrubba succession provides an unambiguous record of central palaeomediterranean base level change during the messinian furthermore the post msc sequence demonstrates a prolonged mediterranean base level rise throughout the late messinian leaving little readjustment necessary in order to restore mediterranean base level to global water levels in basal pliocene times

the messinian salinity crisis past and future of a great challenge for marine sciences forty years after the image of the mediterranean transformed into a giant salty lake was first conceived the fascinating history of the messinian salinity crisis msc still arouses great interest across a large and diverse scientific community early outcrop studies which identified severe palaeoenvironmental changes affecting the circum mediterranean at the end of the miocene were followed by investigations of the marine geology during the 1950s to 1970s these were fundamental to understanding the true scale and importance of the messinian event now after a long period of debate over several entrenched but largely untested hypotheses a unifying stratigraphic framework of msc events has been constructed this scenario is derived mainly from onshore data and observations but incorporates different perspectives for the offshore and provides hypotheses that can be tested by drilling the deep mediterranean basins the msc was an ecological crisis induced by a powerful combination of geodynamic and climatic drivers which had a great impact on the subsequent geological history of the mediterranean area and on the salinity of the global oceans these changed the mediterranean s connections with both the atlantic ocean and the freshwater paratethyan basins causing high amplitude fluctuations in the hydrology of the mediterranean the msc developed in three main stages each of them characterized by different palaeoenvironmental conditions during the first stage evaporites precipitated in shallow sub basins the msc peaked in the second stage when evaporite precipitation shifted to the deepest depocentres and the third stage was characterized by large scale environmental fluctuations in a mediterranean transformed into a brackish water lake the very high resolution timescale available for some late miocene intervals in the mediterranean makes it possible to consider environmental variability on extremely short time scales including in some places annual changes despite this fundamental questions remain some of which could be answered through new cores from the deepest mediterranean basins improvements in seismic imaging and drilling techniques over the last few decades make it possible to plan to core the entire basinal messinian succession for the first time the resulting data would allow us to decipher the causes of this extreme environmental change and its global scale consequences

the origin of evaporitive limestones an example from the messinian of sicily italy a good example of an extensive evaporative carbonate deposit which has altered little since formation is found in the messinian upper miocene evaporites of sicily in this study these messinian carbonates the calcare di base are examined through a combination of field observations together with petrologic mineralogic and stable isotope studies these evaporitic carbonates are found in massive nearly featureless beds both calcite and aragonite commonly composed of automorphic breccias and or weakly layered micrite additionally fine scale features are observed within the carbonates such as small algal stromatolites and algally controlled laminae petrologic study of thin sections reveals ubiquitous algal filaments and grumeleuse to pelletal micrites as the primary components this suggests by analogy to modern hypersaline environments that the original calcium carbonate precipitated as algally controlled aragonite in a hypersaline environment displacive and interbedded halite still present within the deposit in the subsurface in some areas has been leached in others leaving residual breccias cubic voids and halite pseudomorphs the carbonate has been partially calcitized during one or more phases of early diagenesis the diagenetic systems which affected these sediments were not wholly open the halite was removed in some areas early in the sediment s history but after partial lithification probably synsedimentary as indicated by breccias containing well preserved halite voids these breccias lie within a nonhalite bearing micritic matrix later alteration has removed more of the halite leaving cubic void spaces porous layers and halite pseudomorphs filled with calcite celestite and strontianite the presence in some areas of considerable amounts of unaltered aragonite and in other regions of secondary strontium minerals indicate that the systems which affected these sediments were not open ones based on the oxygen isotope values obtained from the unaltered aragonites it appears that the large volumes of calcium carbonate in this deposit were derived from a combination of continual influx of seawater together with a probable contribution from continental sources coming into a restricted hypersaline environment at the margins of the basin the isotopic composition of the altered carbonates suggests that meteoric waters participated in the diagenesis while secondary bacterial processes oxidation sulfate reduction and methanogenesis contributed carbonate ions depleted in carbon 12 to the final product

sedimentary and diagenetic markers of the restriction in a marine basin the lorca basin se spain during the messinian abstract the lorca basin southeastern spain is part of a chain of small marginal neogene basins located in the structurally active betic area the upper miocene messinian sequence is composed of a thick diatomite bearing series tripoli unit overlain by the main evaporites analogous to the classical succession that records the main events during the salinity crisis in the mediterranean region the shallow restricted conditions of this region amplified the sedimentary responses to local and global forcings an integrated approach using sedimentology micropalaeontology stable isotope geochemistry and organic geochemistry has been applied to the tortonian messinian succession of the lorca basin in order to obtain a continuous record of the environmental changes the sediments record two major events which affected the whole mediterranean 1 high levels of productivity that led to the formation of the diatomite bearing deposits in the early messinian tripoli and 2 the messinian salinity crisis with its two major stages represented by the halite and gypsum units both mainly precipitated from marine derived brines the rapid reflooding of the mediterranean by normal marine waters at the base of the pliocene did not reach the lorca basin nor other basins of this part of the betic area instead continental sediments were deposited as a consequence of the regional uplift of se iberia which started close to the messinian pliocene boundary the most prominent feature of this basin concerns the record of its restriction by the time of the deposition of the tripoli unit which led to intercalations of precursor evaporitic layers consisting of ca sulphate deposited in sub aqueous and sabkha conditions interbedded with diatomites this alternation of evaporites and diatomites proves that the lorca basin was periodically restricted and reflooded by marine waters a possible cause for this being relative sea level fluctuations in the mediterranean this strengthens evidence of diachronism that suggests that the onset of the first messinian evaporitic deposition was not synchronous but was dependent on bathymetry and local tectonics high productivity during the early messinian in this basin is demonstrated by the thick deposits of diatomites however stagnation episodes may have occurred during this interval as suggested by the preservation of high amounts of organic matter organic rich shales and the extent of bacterial sulphate reduction which apparently occurred during early diagenesis the formation of organo sulphur compounds replacement of sulphates by carbonates and the high levels of elemental sulphur are by products of diagenetic processes occurring in a restricted hypersaline environment

paleoenvironmental evolution of the eastern mediterranean during the messinian constraints from integrated microfossil data of the pissouri basin cyprus abstract integrated data of calcareous nannofossils as well as planktonic and benthic foraminifera from the pissouri motorway section on cyprus allow the reconstruction of surface and bottom water paleoenvironments of the eastern mediterranean during the interval preceding the messinian salinity crisis msc contrary to deeper water locations where benthic foraminifera faunas are suppressed or absent just after the tortonian messinian boundary sediments deposited at intermediate water depths do contain benthic assemblages from the earliest messinian onwards a development towards increasingly unfavourable paleoenvironments is reflected in the planktonic and benthic microfossil records of the pissouri section and proceeds with rather discrete time steps that can be correlated to sequences throughout the mediterranean shortly after the tortonian messinian boundary a transition is recorded in the sedimentology and the open marine deeper water taxa disappear from the benthic foraminifera assemblages subsequently the diversity of all fauna groups diminishes the changes recorded at species level in both surface water and sea floor dwelling taxa suggest decreasing circulation of the bottom waters associated with changes in the surface waters most likely due to increasing stratification from 6 73 ma onwards our data indicate a prominent change to more restricted conditions and increasing salinity at the sea floor together with intermittently rising surface water salinity the dominance of oligotypic and monospecific assemblages and the frequent shifts in assemblage compositions of all microfossil groups indicate severely stressed environments after 6 4 ma probably related to increased salinity the major changes in paleoenvironmental conditions including oxygen deprivation due to stagnation and hypersalinity can be explained by hydrographical changes in the mediterranean basin which are probably caused by tectonic movements in the rif corridor acting in concert with astronomical cyclicity evaluation of the paleodepth proxies indicates that the depth of the pissouri basin remained rather constant at 300 500 m with a minimum of 200 m until deposition of the barre jaune the transitional interval towards the evaporites and that early shallowing to neritic depths as was proposed before is highly unlikely

alteration of the callovo oxfordian clay from meuse haute marne underground laboratory france by alkaline solution i a xrd and cec study the reaction of the clay fraction of the callovo oxfordian hard shale formation hosting the french underground laboratory site with high ph naoh koh and ca oh 2 solutions has been investigated through closed system experiments at 60 90 and 120 c over 6 24 and 168 h the mineralogical composition of the run samples has been determined using x ray diffraction xrd of randomly oriented powders showing the formation of different species of zeolites analcime chabazite phillipsite and ca silicates tobermorite katoite the phyllosilicates were studied using xrd of oriented preparations and cation exchange capacity measurements detrital or diagenetic mica and chlorite in the 2 m fraction remain unchanged on the contrary the smectite and random illite smectite mixed layer minerals are strongly reactive the expandable layers of montmorillonite type are selectively dissolved while beidellitic ones survive or are transitionally formed

the messinian diatomite deposition in the mediterranean region and its relationships to the global silica cycle abstract diatomites constitute a widely represented lithology in the messinian sections of the circum mediterranean neogene marginal basins although traditionally interpreted as genuine evidence of the gradually restricted conditions that characterized the mediterranean just before the messinian salinity crisis their coeval occurrence with a global intensification of the opaline production in the world oceans late miocene early pliocene biogenic bloom suggests that an integrative analysis of the origins of these sediments is necessary a comprehensive analysis of the geological and paleontological records suggests that the synergistic intervention of abiotic tectonic and climate reconfigurations and biotic expansion of grass dominated opal rich biomes controlling factors may have promoted a remarkable enhancement of silica flux from continents to oceans which in turn can explain the opaline burst that occurred during the late miocene at both the global and mediterranean scale the finely laminated pattern and the rich fossil content of diatomaceous deposits that are usually considered to be byproducts of anoxic conditions are briefly discussed some studies seem to indicate that instead of anoxia the aggregation and sedimentation of diatom tests may play a critical role in these processes the lower messinian diatomites of the mediterranean region are generally interbedded with organic rich sediments sapropels clearly attesting prolonged precessionally controlled periods of basin stratification and bottom water anoxia or hypoxia a causal relationship between sapropel and diatomite deposition in the mediterranean is proposed considering the possible interplay between stratification adapted diatoms and anaerobic bacteria and their respective role in influencing the marine silica cycle

stratigraphy and palaeoenvironmental evolution of the mid to upper palaeozoic succession in northwest peninsular malaysia abstract the stratigraphy of the devonian to permian succession in northwest peninsular malaysia is revised the timah tasoh formation consists of black mudstone containing graptolites and tentaculitids indicating a pragian or earliest emsian age the sanai limestone overlies the timah tasoh formation at sanai hill b and contains conodonts indicating a late devonian frasnian to possibly early famennian age in other places late tournaisian chert of the telaga jatoh formation overlies the timah tasoh formation the overlying kubang pasu formation is predominantly composed of mudstone and sandstone and can be divided into 3 subunits from oldest to youngest 1 chepor member 2 undifferentiated kubang pasu formation 3 uppermost kubang pasu formation the ammonoid praedaraelites tuntungensis sp nov is reported and described from the chepor member of bukit tuntung pauh the genus indicates a late visean age for part of the subunit dropstones and diamictites from the chepor member indicate a glacial marine depositional environment the carbo permian undifferentiated kubang pasu formation consists of similar interbedded mudstone and sandstone the uppermost kubang pasu formation of kungurian age consists of coarsening upward cycles of clastics representing a shallow marine wave and storm influenced shoreline the permian chuping limestone also represents shallow marine wave and storm influenced deposits a mid palaeozoic unconformity separating early late devonian rocks from overlying late devonian carboniferous deposits probably marks initiation of rifting on sibumasu which eventually led to the separation of sibumasu from australian gondwana during the late sakmarian early permian

chronology causes and progression of the messinian salinity crisis the messinian salinity crisis is widely regarded as one of the most dramatic episodes of oceanic change of the past 20 or so million years 1 3 earliest explanations were that extremely thick evaporites were deposited in a deep and desiccated mediterranean basin that had been repeatedly isolated from the atlantic ocean1 2 but elucidation of the causes of the isolation whether driven largely by glacio eustatic or tectonic processes have been hampered by the absence of an accurate time frame here we present an astronomically calibrated chronology for the mediterranean messinian age based on an integrated high resolution stratigraphy and tuning of sedimentary cycle patterns to variations in the earth s orbital parameters we show that the onset of the messinian salinity crisis is synchronous over the entire mediterranean basin dated at 5 96 0 02 million years ago isolation from the atlantic ocean was established between 5 59 and 5 33 million years ago causing a large fall in mediterranean water level followed by erosion 5 59 5 50 million years ago and deposition 5 50 5 33 million years ago of non marine sediments in a large lago mare lake sea basin cyclic evaporite deposition is almost entirely related to circum mediterranean climate changes driven by changes in the earth s precession and not to obliquity induced glacio eustatic sea level changes we argue in favour of a dominantly tectonic origin for the messinian salinity crisis although its exact timing may well have been controlled by the 400 kyr component of the earth s eccentricity cycle

the upper miocene diatomaceous sediments of the northernmost mediterranean region a lamina scale investigation of an overlooked palaeoceanographic archive

the phuket terrane a late palaeozoic rift at the margin of sibumasu abstract it is widely accepted that sibumasu rifted from gondwana in the late palaeozoic but the rifts themselves have not previously been documented in southeast asia this paper identifies the pre middle permian kaeng krachan group of upper peninsular thailand as the infill of one such rift which is given the name phuket terrane indirect evidence suggests the rift infill is several kilometres thick and glacially influenced diamictites are conspicuous in the succession there are significant similarities with the 3 km thick pre middle permian rift infill of the carnarvon basin of western australia east of the khlong marui fault belt the succession is thinner and diamictites are a minor component a tectono stratigraphic model is proposed involving gondwana glaciers dropping their load at the present western margin of the phuket terrane from where it was re sedimented in the rapidly subsiding marine rift basin it is suggested that the khlong marui fault formed part of the eastern boundary of the rift system the three pagodas fault belt similarly juxtaposes different pre middle permian successions rifting ceased in the early permian and a passive margin formed as the mesotethys ocean widened the upper part of the kaeng krachan group and the overlying ratburi limestone representing the post rift sequence

carbonate evaporitic sedimentation during the messinian salinity crisis in active accretionary wedge basins of the northern calabria southern italy abstract this work deals with messinian deposits belonging to the neogene infill of the rossano and belvedere basins respectively developed along the fore arc and the back arc areas of the north calabria accretionary wedge the main goal is to characterize the carbonate and evaporitic sedimentation during the messinian salinity crisis in the general framework of the basin architecture and the interplay between eustatic vs tectonic controlled sea level variations fieldwork integrated with seismic lines and well logs interpretations led to the revision of the general stratigraphy of the basins and the proposal of a new sequential stratigraphic model driven by cyclic sea level variations each cycle repeated at least two times during the messinian salinity crisis time frame begins with a relative sea level fall responsible for the emplacement of prograding wedges composed of terrigenous and evaporitic deposits that subsequently evolve in the deposition of primary basin fill evaporites this phase is followed by open marine transgression due to relative sea level rise that terminates the evaporite formation and predates the development of microbial dominated carbonate platforms associated with shallow water evaporites both basins experienced intense tectonic activity during the messinian which could be responsible for huge basinward sediments exportation and fast decreasing in the accommodation space however this did not substantially influence the development of the systems tracts that considering the basinal architecture have been mainly controlled by eustatic sea level variations in fact two major sea level drops associated with basin restriction and aridity cold conditions seem to have caused the origin of two main evaporitic units as basin fill evaporites while consequent sea level rises and less stressed condition account for two carbonate units with limited evaporites and terrigenous deposition

in situ interaction of cement paste and shotcrete with claystones in a deep disposal context in situ sampling was performed in the andra meuse haute marne france underground research laboratory url allowing the study of two cement based materials claystone interfaces that have undergone 4 to 5 years of interaction the first interface concerned a shotcrete that was sprayed on the wall of an access drift at the laboratory level and the second one a class g cement paste that was injected in a borehole filled from the surface and was intercepted during the excavation of a new gallery in the first case the hydrodynamic conditions were controlled by the ventilation of the drift while in the second the cement paste and claystone materials were considered saturated and far from any mechanical perturbation a multi scale investigation was carried out to identify any evidence of alkaline perturbation in the cement based materials and the claystone chemical mineralogical and textural measurements were thus performed on the different materials in contact at the nanometer to a centimeter scale results showed that all the perturbations resulting from the geochemical contrast between the cement materials and the claystone were limited to a m scale on each side of the interfaces carbonation was observed in the cement materials leading to an opening or a clogging of the porosity according to the hydrodynamic conditions and the formulation of the cement material the distribution of the cation exchange population was also modified in the claystone in contact with the cement paste where a potassium saturation of the exchangeable fraction was identified the originality of the present work is that realistic field controlled samples from the andra url were studied hereby allowing the evaluation of the impact of natural heterogeneities of the in situ experimental conditions that is hydrodynamic conditions engineered damage zone mineralogical variations on the perturbations at the cement paste claystone interfaces an important result is that the clogging of porosity was not homogenous along the interfaces

calcareous nannofossils in extreme environments the messinian salinity crisis polemi basin cyprus the rapidly changing and extreme environmental conditions of the early messinian salinity crisis are reflected in abrupt variations in nannofossil assemblages within the messinian units kalavasos formation from the polemi basin during the messinian sedimentary and microfossil data indicate that the polemi basin was a semi enclosed shallow water basin subject to repeated influxes of marine and freshwater this is supported by the absence of many open marine nannoplankton e g discoaster and by the presence of neritic littoral and freshwater diatoms whilst calcareous nannoplankton are known to occupy near shore habitats they are rarely preserved in such environments due to terrigenous and clastic influx the shallow and eutrophic environments of the messinian polemi basin therefore provide an unusual opportunity to investigate which extinct nannofossil taxa occupied marginal marine environments nannoplankton diversity 3 to 11 species is low in comparison to the open ocean and the assemblages are extremely uneven with high dominance one of five species reticulofenestra minuta reticulofenestra antarctica helicosphaera carteri umbilicosphaera jafari and sphenolithus abies was observed to dominate in all of the assemblages these were broadly distributed marine species but capable of opportunistic behaviour salinity and nutrient levels are thought to be the primary factors controlling the overall nature of the nannoplankton assemblages using the associated diatom and sedimentological evidence we infer the palaeoecology of key nannofossil taxa and speculate on the palaeoenvironments of the messinian polemi basin r antarctica is thought to have dominated in normal salinity mesotrophic shallow water environments h carteri in shallow brackish eutrophic environments u jafari in hypersaline conditions r minuta in eutrophic conditions with an abnormal salinity from brackish to hypersaline and s abies in mesotrophic deeper and normal salinity environments d 2005 elsevier b v all rights reserved

calibrating the duration and timing of the messinian salinity crisis in the mediterranean linked tectonoclimatic signals in thrust top basins of sicily the messinian 9salinity crisis9 which affected the mediterranean represents one of the most dramatic examples of base level fluctuation known in the geological record an amplitude of perhaps 2 km within a stage with a duration of less than 2 ma deposits within the caltanissetta basin of central sicily are used to calibrate the duration and timing of these fluctuations two successions of evaporites termed 9first cycle9 and 9second cycle9 are separated by an inter regional unconformity the first cycle is regionally regressive while the second is transgressive chronostratigraphic calibration of these deposits has been provided by a linked magnetostratigraphic structural and sedimentological study the regression was protracted the earliest evaporites in our study accumulated early in chron c3ar pre 6 88 ma and the youngest accumulated late in chron c3an post 6 0 ma during this interval the basinward shift in coastline was 70 km and in vertical section implies a relative fall in sea level at 0 3 0 4 m ka 1 lowstand probably finally occurred at 5 8 5 5 ma transgression marked by accumulation of the 9second cycle9 deposits which all record reversed magnetizations c3r apparently occurred far more rapidly 200 ka prior to the return to 9normal9 marine conditions in the central mediterranean late in chron c3r local rates of tectonic deformation are relatively slow within the thrust belt which underlies the caltanissetta basin therefore it is likely that the timing and rates of the messinian 9salinity crisis9 on sicily are generally applicable to other basins in the region and help to underpin rates of climate change within this part of the neogene

reply to the comment on carbonate deposition and diagenesis in evaporitic environments the evaporative and sulphur bearing limestones during the settlement of the messinian salinity crisis in sicily and calabria by caruso et al 2015 palaeo3 429 136 162 abstract manzi et al in press took the opportunity offered by our paper to repeat again all the set of ideas supporting an interpretative model of the messinian salinity crisis msc a model they assert to be valid for the whole mediterranean basin what emerges from reading this long comment may be summarized in one criticism of our article we have not systematically applied their interpretative model to our data the aim of our paper was not to promote their ideas but to submit the results of more than 20 years of field studies and petrographical and geochemical analyses on sicilian and calabrian sequences of the messinian calcare di base it is out of our purpose to enumerate again in this reply the data and interpretations we have developed in our paper which disagree with their model and rule out most of their propositions thus we will not reply in detail to this repetitive stream of ideas supporting their model but we want to respond to some general and unfair comments which are often far away from objectivity and rectify some inaccurate assertions about the description of some sections

comment on carbonate deposition and diagenesis in evaporitic environments the evaporative and sulphur bearing limestones during the settlement of the messinian salinity crisis in sicily and calabria by caruso et al 2015 palaeo3 429 136 162 abstract a recent paper by caruso et al 2015 dealing with the calcare di base of sicily and calabria reintroduced an earlier idea that onset on the messinian salinity crisis is diachronous the paper provided a stratigraphic correlation of five sections together with the reference section of falconara and gibliscemi sicily in order to establish the diachronous nature of restricted saline conditions in our opinion their conclusions are not supported by the data and the paper contains some stratigraphic errors that depend on a flawed presentation of the main stratigraphic concepts provided over the past few years covering the deposits of the messinian salinity crisis in sicily in this discussion we challenge the stratigraphic conclusion of caruso et al 2015 holding that a they did not fully consider the different types of deposits included in the calcare di base unit and consequently did not recognize the large scale unconformity at the base of the brecciated limestone calcare di base type 3 b they did not provide univocal criteria for the definition of the onset of the messinian salinity crisis c they hold the idea that the onset of the salinity crisis must be coincident with the onset of the evaporites concept which is not necessarily true d they arbitrarily correlated different evaporitic deposits formed during different stages of the msc e they provided a stratigraphic correlation of the study sections and their tuning with the insolation curve that lacks of reliable stratigraphic constraints consequently they have presented an unreliable schematic evolution of the caltanissetta basin

oxygen isotope composition of diagenetic calcite in organic rich rocks evidence for 18o depletion in marine anaerobic pore water upper cretaceous organic rich carbonates in israel contain benthonic foraminifera and varying amounts of early diagenetic infilling of sparry calcite the sparry calcite has oxygen isotope values down to 9 5 pdb that are significantly lower than those of the coexisting skeletal calcite averaging 2 pdb low 18o values are very common in carbonates that are associated with organic matter these occurrences are conventionally explained as being due to carbonate formation under conditions of low salinity and or elevated temperature on the basis of petrographic data and local geologic evidence however none of the conventional explanations can be applied in this case we advance an alternative model that relates the light oxygen compositions of the diagenetic calcite to depletion of 18o in pore water of normal salinity the proposed operating mechanism is a direct consequence of organic matter decomposition in the sulfate reducing zone being inherent to reducing marine environments this model can be applied to many organic rich rock associations

carbonate deposition and diagenesis in evaporitic environments the evaporative and sulphur bearing limestones during the settlement of the messinian salinity crisis in sicily and calabria abstract the depositional and diagenetic processes involved in the formation of carbonates in the evaporitic environment of the messinian salinity crisis are investigated in southern italy sicily and calabria strong differences are observed between the studied sections that reflect specific depositional and diagenetic evolution in the interconnected sub basins resulting from the syn sedimentary tectonic fragmentation of the central sicilian and calabrian domains these carbonates formed diachronously in restricted perched sub basins between the tripoli formation and the hypersaline settings of the msc the calcare di base cdb that can be interbedded with gypsum layers occurs rhythmically at the transition between the upper part of the tripoli formation and the massive gypsum and at places synchronously with the deposition of the lower gypsum unit it deposited initially as primary peloidal and microbial limestones but their original structure and mineral composition were modified by the superimposition of early to late diagenetic processes the first diagenetic step was the development of interstitially grown gypsum and halite crystals from trapped saturated brines that locally led to the formation of salt beds the sulphur limestone sl resulted from the activity of sulphate reducing bacteria that occurred locally in the deeper parts of the various basins where anoxic bottom waters favoured microbial processes fuelled by biogenic methane and crude oil and caused the carbonate replacement of gypsum and the formation of native sulphur the migration of hydrocarbon and h 2 s rich fluids caused the epigenetic dissemination of sulphur and a late diagenetic carbonate replacement of the gypsum later influxes of continental fresh waters were responsible for the dissolution of the halite crystals and their replacement by sparry calcite the vugs formed during both the gypsum calcite conversion and the halite dissolution either remained empty or were filled with calcite celestine fibrous silica anhydrite secondary gypsum and native sulphur the initial accumulation of fine grained carbonate and gypsum sediments was strongly destabilised by volumetric changes resulting from mineral replacements and fluidisation processes their superimposition explains the vuggy and boxwork like textures in situ brecciation and lateral displacement which are responsible for the chaotic organisation without necessarily involving basin scale re sedimentation in the form of debris flows

transition from marine to hypersaline conditions in the messinian tripoli formation from the marginal areas of the central sicilian basin abstract three sections of the early messinian tripoli formation from the northern and southern margins of the central sicilian basin serra pirciata torrente vaccarizzo and marianopoli have been studied with the aim to reconstruct the sedimentary and environmental changes which occurred during the transition between marine conditions and the evaporitic events of the salinity crisis recorded in the overlying calcare di base formation a detailed biostratigraphic and cyclostratigraphic study provided the opportunity of cycle by cycle correlations between the marginal sections and the reference section of falconara the main paleoenvironmental changes are recorded by 1 the evolution of calcareous microfossils towards low diversity and their complete disappearance 2 the composition of the carbonate fraction which commonly changes from calcite mostly related to calcareous microfossils to authigenic carbonate phases consisting of either calcite dolomite and or aragonite 3 the appearance of shallow water deposits and evaporite pseudomorphs 4 the variation of the stable isotope composition of the carbonate fraction indicative of large fluctuations of the freshwater dilution evaporation balance with a general trend towards hypersaline conditions both mineralogical and isotope data indicate that the dolomite precipitated generally from concentrated pore waters while other carbonates formed in the water column submitted to large fluctuations of salinity except locally the increase in salinity did not reach concentrations high enough to precipitate significant volumes of evaporites as during the deposition of the overlying calcare di base the transition from normal marine to hypersaline conditions is recorded diachroneously in the three sections respectively in cycle 34 6 32 ma at serra pirciata cycle 42 6 15 ma at torrente vaccarrizzo and cycle 44 6 12 ma at marianopoli these changes represent the hydrological and sedimentary response to the fragmentation of a large marine basin into different subbasins which ended in the more or less complete closure recorded by the deposition of the overlying evaporite rich calcare di base fm true onset of the evaporitic event two hypotheses not exclusive may explain this change either the regional consequence of the compressive tectonics or the incipient drop of the global sea level which led to the salinity crisis our results confirm that the salinity crisis was preceded by evaporative episodes in the evolution towards hypersaline conditions which occurred diachroneously as a response to the diversity of paleogeographical settings even if the paroxysmal phase seems to have affected the basin at the same time

microbial mediated pre salt carbonate deposition during the messinian salinity crisis calcare di base fm southern italy abstract a multi scale analysis of sedimentary carbonate facies and post sedimentary diagenetic features of the calcare di base formation the precursor to evaporites in upper messinian successions of northern calabria and central sicily has revealed their microbial bio mediated origin massive to laminated microbial boundstones represent the most common sedimentary facies forming flat to low relief cm to m scale stromatolitic and thrombolitic bodies the fabric of the micrite varies from peloidal to aphanitic and almost always preserves filamentous bacteria which characterized the original microbial mat the mat was dominated by sulphur oxidizing bacteria belonging to the thiotrichaceae but there is evidence for a more complex community with sulphate and or nitrate reducing bacteria all being responsible for the mediation of the carbonate precipitation microbial boundstones are rich in pseudomorphs of ca sulphate and halite which formed during the deposition of the microbial carbonate layers of primary gypsum are interbedded locally with carbonates suggesting the presence of restricted marine conditions the stable o and c isotopic composition of the carbonates that vary from dolomite to aragonite and calcite suggests a complex interplay between arid to humid climatic changes expressed cyclic interbedding of the carbonate with marl marlstone later diagenetic events mainly consist of phreatic meteoric recrystallization and cementation although considered as diachronous the microbial carbonates can be mapped out over a distance of more than 500 km across southern italy this indicates near constant environmental conditions upon the central mediterranean shelf at the beginning of the salinity crisis deposition of the extensive subaqueous microbial deposit that largely comprises the calcare di base is envisaged to have taken place across a shallow to moderate depth platform with local slopes into deeper water areas where some resedimentation occurred

late tortonian early messinian stepwise disruption of the mediterranean atlantic connections constraints from benthic foraminiferal and geochemical data abstract late miocene marine land based sections in the mediterranean area contain important information on the prelude to the messinian salinity crisis msc integrated bio magneto tephra and cyclo stratigraphy allows for bed to bed correlations of sections throughout the mediterranean and its borderlands and enables correlation with extra mediterranean atlantic sites benthic foraminiferal and geochemical data from five sections were compared to literature data and indicate that a restriction of the mediterranean from the atlantic ocean started during the late tortonian b the continuous development towards the msc started as early as 7 2 ma in the deeper parts of the basin and was enhanced by astronomical forcing and 3 the onset of the msc must have been to a large extent related to differential vertical movements at the betic and rifian corridors the miocene connections between the mediterranean and the atlantic

15 years of in situ cement argillite interaction from tournemire url characterisation of the multi scale spatial heterogeneities of pore space evolution the solution selected by some countries to isolate radioactive wastes from the biosphere for up to one million years in deep geological repositories includes a multi barrier disposal design with steel canister bentonite and cement materials the geochemical contrast between such materials and the host rock formation creates perturbations potentially altering the confinement properties of the formation in this context the french institute for the radiological protection and nuclear safety irsn have developed an in situ experimental programme based on the study of cement argillaceous formation interfaces in their underground research laboratory at tournemire aveyron france an in situ engineered analogue of a cement clay rock interface which has undergone 15 years of interaction has been characterised such important interaction time for an in situ engineered analogue provides a bridge between laboratory derived data and the long time scale of safety assessment modelling as the mineralogical and petrological investigations have already been published this work presents for the first time a quantitative characterisation of the spatial distribution of the porosity in the cement and the clay rock in terms of time scale and design interfaces have been characterised using an autoradiography technique in addition to petrophysical measurements this technique enables visualisation and quantification of the spatial distribution of the porosity using 2d mapping of decimetric scale specimens thus autoradiographs allow highlighting the relationship between the field heterogeneities and the pore space evolution in each material in contact moreover the porosity measurements show a clogging of the porosity in the clay rock while the porosity increases in the cement the extension of the porosity evolution extends to a centimetre on both sides of the interface but is heterogeneously distributed in space as a function of the fissure network and interface geometries the connected fissure network visualised using autoradiography in the clogged area could permit solute e g radionuclide transport and may also be interpreted as an evolution of the mechanical properties of the clay rock formation upon alkaline perturbation this set of data with the spatial quantification of the porosity in both cement and clay materials will be useful to constrain reactive transport modelling and thus to predict long term evolution of an engineered barrier

benthic foraminiferal proxies of environmental changes during the pre messinian salinity crisis of the sinis basin w sardinia mediterranean sea abstract the messinian succession cropping out in a marginal basin of the mediterranean sea sinis basin w sardinia was studied in its benthic foraminiferal content in order to investigate the main palaeoenvironmental changes occurring a shallowing upward depositional trend from an upper bathyal circalittoral environment to a coastal lagoon was recognized during the pre messinian salinity crisis in the lower part of the analyzed succession capo san marco formation upper bathyal circalittoral conditions are suggested by species with a wide depth range such as cibicidoides pseudoungerianus melonis pompilioides oridorsalis umbonatus bolivinids and buliminids in the middle part of this formation the progressively shallowing environment is indicated by the low abundance of planktonics coupled with the upward increase of shallow water epiphytic species lobatula lobatula elphidium crispum e macellum ammonia beccarii hanzawaia boueana the progressive marine restriction led to the development of hypohaline conditions typical of lagoonal environments as suggested by ammonia tepida and oligotypic macrofaunas the succession stops with the deposition of laminated limestones barren in fossils sinis laminated limestone formation a mixed siliciclastic carbonate platform torre del sevo formation characterized by fluvial deposits intercalated in the marine succession developed as suggested by benthic foraminifera ostracods very rare planktonic species and macrofaunas sinis laminated limestone formation and torre del sevo formation constituted part of the terminal carbonate complex strongly eroded by the messinian erosional surface mes at its top the palaeoecological conditions in the sinis basin were intermittently suitable for sustaining full marine biota indicating that this marginal basin was not constantly desiccated during the pre messinian salinity crisis

cyclostratigraphy and astrochronology of the tripoli diatomite formation pre evaporite messinian sicily italy the ongoing debate about the messinian salinity crisis in the mediterranean is fuelled in part by the lach of an adequate time control the most accurate and at the same time detailed constrains are nowadays provided by the astronomical dating technique here we present an astronomical age model for the cyclically bedded tripoli diatomite formation on scily pre evaporite messinian italy based on an intergrated stratigraphic study of three key sections falconara gibliscemi and capodarso characteristic sedimentary cycle pattenrs allow i the sections to be cyclostratigraphically correlated the bed to bed correlations being confirmed by high resolution planktonic foraminiferal biostratigraphy and ii the tripoli cycles to thecalibrated to the astronomical record despite minor misfits the correctness of thetuning is evident from the match between precession obliquity interference in the astronomical target and its reflection in the sedimentary cycle record the tuning provides absolute astronomically dated at 7 005 ma indicating that the onset of diatomite formation is diachronous in the mediterranean since itstarted 300 000 years earlier on sicilt than on gavdos south of crete the top of the tripoli and thus the onset of the salinity crisis proper on sicily arrives at 5 98 ma

archaeal lipids record paleosalinity in hypersaline systems abstract we present an ecologically based biomarker method for estimating past salinity especially in hypersaline conditions the relative amounts of acyclic diether and tetraether membrane lipids synthesized by archaea correlate with salinity from 0 250 practical salinity units psu in modern settings we examined the preservation of this lipid biomarker salinity relationship in ancient sedimentary organic matter using samples from two sequences of marls and diatomites deposited just prior to the messinian salinity crisis salinity estimates were consistent with expected absolute salinity as well as the amplitude of variations leading up to the messinian salinity crisis this lipid biomarker approach to salinity reconstruction complements existing paleosalinity proxies because i archaea survive and thrive over a broad salinity range well beyond that of haptophyte algae and other plankton which form the microfossil record and ii it provides fine salinity resolution for the wide range broadly defined as hypersaline with the proxy there is the potential to provide novel insights into salinity variation within desiccating basins in climatically sensitive seas e g dead sea permian delaware basin evolution of brines timing of onset of hypersaline conditions and evaporite deposition

high resolution stable isotope stratigraphy from bulk sediment a high quality 18 o record has been obtained from a deep sea core in the somali basin in a water depth of 4020 m well below the foraminiferal lysocline by analyzing bulk sediment instead of picked foraminifera in some areas this may be a valuable tool for extending the applicability of the 18 o stratigraphy for obtaining data by a less laborintensive procedure and for conserving valuable core material additionally we draw attention to the need for more data on 6 3c in bulk carbonate if we are to fully utilize the ocean 6 3c record either in relation to long term global carbon budget or in relation to changes in carbon cycling in the ocean and its effect on atmospheric pco 2

quaternary paleo oceanography pteropod preservation and stable isotope record of the red sea abstract an abundance of pteropod species their mode of preservation and stable isotope ratios of carbon and oxygen in benthic and planktic foraminifera have been determined in core md76 140 from the northern red sea isotopic data and benthic foraminiferal species indicate changes in o2 concentration in the bottom sediments the glacial stages are characterized by an almost anoxic bottom while the interglacial bottom was generally well ventilated in general very well preserved pteropod shells occur in glacial oxygen depleted intervals and also on recent well ventilated bottoms in the interglacial stages the preservation deteriorates and in the most extreme cases there is a complete dissolution of the aragonitic shells in these cases most of the assemblage is lost and the only traces of the original shells are their internal molds these are cemented with high magnesium calcite hmc which is a more stable carbonate phase in bottom sediments of the interglacial dissolution of aragonite discriminates between large and small shells the latter tend to be removed completely while the larger ones may be preserved as internal hmc molds limacina inflata is more readily molded than l trochiformis and thus its relative abundance increases in poorly preserved assemblages the state of aragonitic shell preservation depends on the degree of organic matter combustion in the sediments well preserved shells occur in sediments where the supply of organic matter is limited and o2 levels are high preservation deteriorates with increasing supply of organic carbon o2 consumption and increasing production of co2 in this case the dissolved carbonate is reprecipitated as hmc cement with further increase in organic matter supply and reduced ventilation nearly all oxygen is consumed and no3 and subsequently so42 become the oxidizing agents this is followed by an increasing carbonate alkalinity and excellent aragonitic shell preservation

late miocene paleoenvironmental changes in north africa and the mediterranean recorded by geochemical proxies monte gibliscemi section sicily abstract the astronomically tuned marls of the monte gibliscemi section sicily constitute an archive to trace the late miocene palaeoenvironmental conditions 9 7 7 0 ma in north africa here we have utilised carbonate content and al normalised geochemical proxies to trace changes in terrigenous source area and bottom water ventilation the terrigenous input into the section is dominated by north african river systems draining into the eastern mediterranean the proxy parameters indicate that the palaeoenvironmental conditions in north africa were humid from 9 5 ma onward with high fluvial input to the mediterranean increases in the si al and mg al ratios occurred from 8 4 to 8 2 ma and from 8 05 to 7 75 ma with maximum values similar to those of messinian diatomites these peaks indicate conditions of enhanced biosiliceous productivity and the presence of authigenic clay formation sluggish water circulation in the mediterranean during those times is inferred from the mn al and v al behaviour late miocene changes of the betic southern spain and rifian morocco mediterranean atlantic gateways are interpreted as the driving force for the changes in water circulation and the transgression associated with the opening of the rifian corridor is interpreted to occur at 7 8 ma

climatic and oceanographic isotopic signals from the carbonate rock record and their preservation stable isotopic data from marine limestones and their constituent fossils and marine cements can provide quantitative evidence for changes in global climate and ocean circulation oxygen isotopic data can indicate changes in temperature and ocean composition whereas stratigraphic variation in carbon isotope ratios may reflect changes in the carbon cycle that can be linked to changes in oceanic productivity and atmospheric greenhouse gases terrestrial carbonates meteoric cements calcretes and speleothems similarly offer significant potential for understanding the evolution of terrestrial climates by providing evidence for the composition of rainwater and the nature of vegetative cover primary environmental isotopic signals may be obscured by the effects of post depositional diagenetic alteration cementation and replacement reactions can take place in a wide range of diagenetic environments the diagenetic history of an individual limestone is determined by a combination of its mineralogical diagenetic potential and depositional setting together with subsequent changes in relative sea level and burial history carbon isotopic values are less prone to alteration during diagenesis than oxygen values but shifts can be significant where organogenic carbon is incorporated linear covariation of carbon and oxygen values is not a reliable indicator of diagenetic alteration water rock interaction and fluid mixing may produce non linear distributions attempts to determine long term changes in climatic and oceanographie conditions through isotope stratigraphy of shallow water limestones must include an assessment of the diagenetic history of the materials analysed petrographic examination using conventional microscopy backed up where appropriate by cathodoluminescence and scanning electron microscopy together with elemental and strontium isotopic analysis can help to identify the effects of diagenetic alteration where material with a range of different degrees of alteration is preserved in the same sediment it may be possible to compare patterns of isotopic and elemental variation and to attempt to unravel the effects of diagenesis in order to determine primary environmental isotopic signals recent research has shown that these techniques can be successfully employed in both phanerozoic and precambrian sediments

the beginning development and termination of the middle miocene badenian salinity crisis in central paratethys abstract middle miocene badenian evaporites of the carpathian region are underlain and overlain by deep water deposits the onset of evaporite deposition was sudden but not synchronous in all facies zones and the deposition of evaporites was controlled by the evolution of carpathian orogen in the carpathian foredeep and most probably in other basins the badenian evaporites represent the lower part of the nn6 zone halite and associated deposits in the central part of the badenian evaporite basin show the same facies successions and marker beds can be traced across and between individual basins characteristic marker beds made it possible to correlate various facies zones of the marginal ca sulfate platform these marker beds seem to reflect events that may be related to sudden and widespread changes in water chemistry which in turn imply major changes in basin hydrology the onset of the evaporitic deposition in the carpathian foredeep was clearly diachronous and the evaporites deposited in the basin centre preceded the beginning of evaporite sedimentation in the marginal basin however depositional history in the marginal basin and the basin centre was the same a general transgressive sequence of evaporites found in the carpathian foredeep resulted from the migration of facies zones induced by the nappe movement isotopic studies of badenian foraminifers occurring below evaporites suggest that the interrupted communication of the paratethys with the ocean was a consequence of eustatic sea level fall possibly related to climatic cooling and it was coupled with a tectonic closure of connection with the tethys thus both tectonics and eustacy have contributed to the origin of salinity crisis sedimentological and geochemical data indicate recycling of evaporites throughout most of the evaporite deposition the recycling at the end of gypsum deposition in the marginal sulfate platform was accompanied by a change in the hydrology of the central paratethys that was tectonically driven and possibly related to the block tectonic phase manifested in the marginal part of the carpathian foredeep basin the change in hydrology implied the dilution of brines by inflowing marine water and this terminated the middle miocene badenian salinity crisis the onset of the badenian salinity crisis shows great similarities to the onset of the messinian salinity crisis and the terminations of both crises were different

calcareous nannofossil and foraminiferal trace element records in the sorbas basin a new piece of the messinian salinity crisis onset puzzle abstract the messinian salinity crisis msc was an extreme event that affected the mediterranean sea during the late miocene leading to massive evaporite deposition across the basin here we focus on the perales section sorbas basin western mediterranean using calcareous nannofossil cn and foraminiferal geochemical analyses to trace the paleoenvironmental dynamics culminating in the msc onset orbital and tectonic forcing drove the cn fluctuations that correlated with the lithological quadripartite precessional cycle our integrated analysis reveals that cyclical sapropel deposition was triggered by an increase in marine productivity followed by an increase in freshwater input and the development of a deep chlorophyll maximum dcm the overlying marl records the protracted freshwater input that led to the shallowing of the dcm decreasing organic carbon export and promoting seafloor re oxygenation stratification acting as a barrier trapped part of the river sourced nutrients below the photic zone the subsequent gradual decrease in temperature promoted the disruption of the stratification mixing nutrients upward into the photic zone and promoting diatom proliferation and preservation when the reservoir of dissolved silica was exhausted bioturbated marls were deposited at the top of the cycle in the last pre evaporitic cycle ua34 the usual lithological cyclicity is obliterated however the precessional footprint is revealed by cn fluctuations suggesting that sapropel like deposition lasted for most of the cycle this cycle also records a succession of cn abundance peaks msc onset bioevent as already recorded in several mediterranean sections approximately at the msc onset suggesting that the same paleoenvironmental changes triggered the evaporitic phase in the whole mediterranean this bioevent marks the last step of water exchange reduction with the atlantic restriction pulse which increased the sensitivity of the mediterranean to freshwater input and associated nutrient delivery culminating in a further increase in marine productivity

influence of reaction kinetics and mesh refinement on the numerical modelling of concrete clay interactions large quantities of cements and concretes need to be incorporated in geological disposal facilities for long lived radwaste an alkaline plume diffusing from an aged concrete ph 12 5 through argillite type rocks has been modelled considering feedback of porosity value variations on transport properties using the reactive transport code toughreact the mineralogical composition of the argillite is modified at the interface with the concrete diffusion of cementitious elements leads to rapid and strong porosity occlusion in the argillite numerical results show that both reaction rates and spatial refinement affect mineralogical transformation pathways the variations in porosity and the extension of the zone affected by the alkaline perturbation are compared at different times the major effects of mineral precipitation under kinetic constraints rather than local equilibrium are a delay in the porosity clogging and an increase in the extension of the alkaline perturbation in the clay formation the same time delay rise for the porosity occlusion also appears for the roughest spatial resolutions a simulation as representative as possible of temporal and spatial scales of cementation processes must then be supported by more comparative data such as long term experimental investigations or natural analogues

a review of basin wide calcareous nannofossil bioevents in the mediterranean at the onset of the messinian salinity crisis abstract during the messinian 7 2 5 3 ma the mediterranean area experienced fast and deep climatic and eustatic structural changes the stratigraphic framework for this interval is relatively well constrained and the beginning of the messinian salinity crisis msc dated at 5 971 ma suggests a duration of at least 1 2 ma for the pre evaporitic messinian that is the object of this study a number of sites faneromeni pissouri polemi basin kalamaki falconara fanantello lemme pollenzo govone moncalvo blanc valleron et al 2002 wade and bown 2006 kouwenhoven et al 2006 morigi et al 2007 lozar et al 2010 2018 dela pierre et al 2011 karakitsios et al 2017 show similar behaviour of the calcareous nannofossil record where several peaks of sphenolithus spp are recognised at different levels in each of the section this paper compares the calcareous nannofossil data from six different sections across the northern and eastern mediterranean area encompassing the onset of the msc interestingly a tight succession of bioevents sphenolithus abies helicosphaera carteri umbilicosphaera rotula rhabdosphaera spp is recorded in all the sections analysed and appears to correlate precisely among the investigated sites approximating the onset of the messinian salinity crisis thus offering the possibility to use these as bioevents for regional correlation

evaporite carbonate cycles of the messinian sicily stable isotopes mineralogy textural features and environmental implications abstract an investigation of the genetic environment of laminar and massive gypsum and intercalated carbonates messinian central sicily has been carried out by means of isotopic textural and mineralogical analyses the oxygen and hydrogen isotope compositions of crystal water from the laminar gypsum indicate primary precipitation of the sulfate from marine waters concentrated by evaporation the isotopic data also show compositional changes due to periodic influx of continental waters into the deposition basin in the laminar gypsum and interlayered dolostones we find a micritic near to or stoichiometric dolomite showing very positive 18o and negative 13c values which are consistent with formation of this carbonate at a very early diagenetic stage by precipitation from highly evaporated interstitial waters depleted in so4 ions by gypsum cr stallization and concurrent bacterial so4 reduction open marine water incursions probably led to the deposition of carbonate layers overlying the laminar gypsum these contain abundant aragonite whose textural features and isotopic composition suggest precipitation in shallow and quiet marine waters slightly enriched in 18o by evaporation the isotopic data of a euhedral and ca rich dolomite formed later than the aragonite may reflect further influxes of continental waters into the basin on the basis of 18o and d values the massive gypsum in the upper portion of the sedimentary sequence seems to have been formed by hydration of anhydrite

paleoenvironmental change in a precession paced succession across the onset of the messinian salinity crisis insight from element geochemistry and molecular fossils abstract in marginal mediterranean sub basins the early phase of the messinian salinity crisis msc is recorded by cyclic successions of gypsum and shales which in deeper parts of the sub basins make lateral transition into organic rich shales marls and carbonates the cyclic stacking pattern of the gypsum bearing sequences is assumed to reflect periodic paleoenvironmental change induced by precession driven climate perturbations with the assumption that shales reflect humid climate precession minima while gypsum reflects arid conditions precession maxima however this correlation has not been verified to date mostly because of the scarcity of microfossils the most commonly used tools for the reconstruction of precession driven paleoenvironmental change such change can instead be reconstructed through the study of the deeper water counterparts of gypsum marly and carbonate layers with geochemical indicators major and trace elements molecular fossils which provide insight on climate and aquatic productivity we used this approach to study a section from the piedmont basin nw italy where the onset of the msc is archived in a sequence of organic rich sediments this sequence displays distinct lithological cyclicity evidenced by the repetition of couplets of organic rich shales and marls either bioturbated in the pre msc part of the section or laminated during the msc the influence of orbitally driven precession climate oscillations is demonstrated by fluctuations of ti al si al mg al k al zr al and ba al ratios that are in phase with lithological cyclicity these fluctuations are interpreted to reflect alternation of humid shales deposited during precession minima and arid bioturbated and laminated marls deposited during precession maxima phases dominated by fluvial and aeolian transport of detrital material respectively the cyclicity of the element ratios is mirrored by changes in organic carbon content and molecular fossil inventory in particular the distribution of long chain n alkanes and their degree of preservation reveal that humid phases at times of precession minima were typified by the maximum input of degraded terrestrial organic matter driven by enhanced riverine runoff which promoted water column stratification coeval increase in ba content a common paleoproductivity proxy agrees with enhanced nutrient supply during humid periods promoting phases of eutrophication in the basin lithological and geochemical changes are observed in msc sediments deposited at times of precession maxima evidenced by the replacement of pre msc bioturbated marls by laminated marls rich in filamentous fossils corresponding to the remains of probable colorless sulfide oxidizing bacteria such changes reflect an intensification of water column stratification after the onset of the msc possibly related to the combined effect of persistent freshwater inflow and basin isolation preluding the advent of gypsum precipitation

molecular fossils and other organic markers as palaeoenvironmental indicators of the messinian calcare di base formation normal versus stressed marine deposition rossano basin northern calabria italy a multidisciplinary study has been carried out on the late miocene messinian calcare di base formation in northern calabria italy with the aim of understanding the depositional conditions of these enigmatic carbonate sediments that have been interpreted as evaporitic or diagenetic limestone the research has been developed through sedimentological microfacies organic petrography and geochemical analyses palynofacies rock eval pyrolysis and gas chromatography mass spectrometry the carbonates studied preserve their original mineralogy aragonite and microstructure the prevailing microfacies consists of clotted peloidal micrite with antigravitative fabric larger and darker cylindrical subcylindrical micritic grains attributable to faecal pellets are more or less randomly dispersed in the peloidal micrite the faecal pellets have been ascribed to copepods because zooclasts of these arthropods were observed in the palynofacies bright epifluorescence characterizes the faecal pellets and peloidal micrite indicating their high content of organic matter detrital and stromatolitic microfacies occur rarely around a few percent the detrital microfacies is characterized by silt sized grains organized in thin sometimes bioturbated graded laminae the stromatolitic microfacies shows planar to gently curved wrinkled laminae organized in dark and light couplets the associated sedimentary organic matter shows low maturity and preserves the original signatures of the source organisms rock eval pyrolysis revealed a transitional composition between type ii and type iii kerogen suggesting a mixture of marine and terrigenous organic matter input the molecular biogeochemical data indicate three main biological signatures algae bacteria and higher plants organic markers together with sedimentary evidence indicate a marine depositional scenario influenced by freshwater input rather than evaporitic concentration we conclude that the most probable bacterial process involved in carbonate precipitation of the calcare di base considering the freshwater input and consequent probable enrichment in organic matter and ca2 ions is ammonification of amino acids in aerobic conditions

flocculent layers and bacterial mats in the mudstone interbeds of the primary lower gypsum unit tertiary piedmont basin nw italy archives of palaeoenvironmental changes during the messinian salinity crisis abstract the recognition of peculiar laminated layers atypically rich in a biogenic intrabasinal component in the mudstone intervals from the messinian late miocene primary lower gypsum unit 5 97 5 60 ma of the piedmont basin nw italy provides information on the palaeoenvironmental evolution at precessional insolation maxima these cyclic layers consist of irregular alternation of cm thick grey terrigenous laminae and whitish composite packets the latter is in turn composed of sub mm thick wrinkled dolomite rich laminae that alternate with terrigenous ones two types of layers can be distinguished i peloidal layers composed of faecal pellets and irregular diatom rich aggregates interpreted as marine snow floccules and ii filament bearing layers composed of interwoven filaments up to 150 m across corresponding to remains of beggiatoa like giant sulphide oxidising bacteria by comparison with present day settings the peloidal layers are interpreted as flocculent layers deposited on anoxic sea bottoms following episodes of phytoplankton bloom in the upper water column the filament bearing layers are considered as chemotrophic microbial mats growing on dysaerobic sea bottoms the uncommon preservation of both kinds of layers is the result of extensive dolomite precipitation in the shallow subsurface induced by bacterial sulphate reduction the laminated layers are the first reported example of a high frequency climate driven cyclicity in the non evaporitic portion of the primary lower gypsum unit their stacking pattern within the mudstone intervals reflects the gradual increase of the oxygen content of bottom waters during the humid precessional hemicycle culminating with gypsum deposition at the onset of the arid phase

the end of the messinian salinity crisis evidences from the chelif basin algeria how did the messinian salinity crisis end is a matter of intense debate between two opposite concepts i e the generalised dilution event the so called lago mare followed by the sudden restoration of the marine conditions at the base of the zanclean or the early partial or complete marine refill that would have happened earlier during the upper messinian the chelif basin of northwestern algeria one of the greatest messinian marginal basins of the mediterranean provides an exceptional opportunity to study in detail how this major paleoenvironmental change occurred through continuous sedimentary records of the miocene pliocene boundary five sections representative of both the central and marginal areas of the chelif basin were analysed in detail for sedimentology mineralogy foraminifera and ostracod assemblages and stable isotope composition of carbonates the late messinian deposits exhibit a great lithological variability with predominant clastic deposits sandstones siltstones conglomerates carbonates with in some marginal areas large slided masses of lower messinian tripoli unit that settled just before the base of the zanclean most sediments are either azoic or contain microfossils typical of hyposaline conditions sometimes mixed with benthic foraminifera known to be adapted to stressed environments and even to lacustrine conditions fewer types of sediment contain assemblages of planktonic foraminifera including typical messinian species which are thought to be reworked in contrast diversified communities of benthic and planktonic foraminifera returned suddenly at the base of the zanclean the messinian pliocene transition was marked by an abrupt change of the 18o values of carbonates from variable but predominantly negative values characteristic of low salinity conditions in the upper messinian to higher and more stable values in the zanclean typifying marine conditions the southern margin continued however to be submitted to large inputs of continental waters the beginning of the marine inundation was a transitional period with poorly diversified assemblages of planktonic foraminifera and benthic communities tolerant to oxygen deficient bottom conditions more stable marine conditions with better bottom water ventilation were set up after a lag time which would roughly correspond to a precession cycle except for the more marginal areas where conglomerates and erosional features are observed the restoration of marine conditions occurred without any significant erosion in the more central areas where the contact is well marked by strong burrowing activity by benthic organisms this indicates the rapid substitution in the basin of brackish waters by marine waters both mixing of these two kinds of waters and permanence of freshwater inputs in the initial stage of the pliocene transgression may explain why the community of marine planktonic foraminifera introduced by the inflowing atlantic waters hardly survived in such unfavourable ecological conditions in the mediterranean and reached a normal development later when more stable marine conditions settled this study and the comparison with other sections from both marginal and deep mediterranean basins confirm that the lago mare was a widespread dilution event that affected the whole mediterranean at the end of the messinian which was abruptly interrupted by the sudden marine inundation at the base of the zanclean

alteration of the callovo oxfordian clay from meuse haute marne underground laboratory france by alkaline solution ii modelling of mineral reactions abstract one of the french options for the final disposal of high level radioactive waste is a deep geological repository the callovo oxfordian formation in the meuse and haute marne france was proposed by the french agency for the management of radioactive wastes andra to be the site of a research laboratory in order to evaluate in situ the interaction between the host formation and the engineered barriers in the previous experimental part secondary minerals such as zeolites tobermorite and katoite have been observed after the alteration of the callovo oxfordian clay under alkaline conditions three different reactions of phyllosilicates alteration have been proposed as a function of both ph and chemical composition of the reacting solutions the aim of this work was to simulate the reaction between the callovo oxfordian clay and high ph solutions in order to validate the proposed alteration reactions from experimental data the thermodynamic modelling of stability relationships among minerals in the callovo oxfordian clay was performed using the solution speciation solubility modelling code kindis at 120 c for different chemical media naoh koh and ca oh 2 input data were the mineralogical composition of the

the response of water column and sedimentary environments to the advent of the messinian salinity crisis insights from an onshore deep water section govone nw italy

carbonate stromatolites from a messinian hypersaline setting in the caltanissetta basin sicily petrographic evidence of microbial activity and related stable isotope and rare earth element signatures lower messinian stromatolites of the calcare di base formation at sutera in sicily record periods of low sea level strong evaporation and elevated salinity thought to be associated with the onset of the messinian salinity crisis overlying aragonitic limestones were precipitated in normal to slightly evaporative conditions occasionally influenced by an influx of meteoric water evidence of bacterial involvement in carbonate formation is recorded in three dolomite rich stromatolite beds in the lower portion of the section that contain low domes with irregular crinkly millimetre scale lamination and small fenestrae the dominant microfabrics are i peloidal and clotted dolomicrite with calcite filled fenestrae ii dolomicrite with bacterium like filaments and pores partially filled by calcite or black amorphous matter and iii micrite in which fenestrae alternate with dark thin wispy micrite the filaments resemble beggiatoa like sulphur bacteria under scanning electron microscopy the filaments consist of spherical aggregates of dolomite interpreted to result from calcification of bacterial microcolonies the dolomite crystals are commonly arranged as rounded grains that appear to be incorporated or absorbed into developing crystal faces biofilm like remains occur in voids between the filaments the dolomite consistently shows negative d 13 c values down to 11ae3 and very positive d 18 o mean value 7ae9 that suggest formation as primary precipitate with a substantial contribution of organic co2 very negative d 13 c values down to 31ae6 of early diagenetic calcite associated with the dolomite suggest contribution of co2 originating by anaerobic methane oxidation the shale normalized rare earth element patterns of sutera stromatolites show features similar to those in present day microbial mats with enrichment in light rare earth elements and m type tetrad effects enrichment around pr coupled to a decline around nd and a peak around sm and eu taken together the petrography and geochemistry of the sutera stromatolites provide diverse and compelling evidence for microbial influence on carbonate precipitation