present status of the astronomical polarity time scale for the mediterranean late neogene sedimentary cycles may reflect orbitally induced climate oscillations and can then be used to construct astronomical time scales following the initial tuning of the late pleistocene the anchored astronomical time scale was extended to the base of the pliocene using palaeoclimatic records from ocean drilling project odp sites in the eastern equatorial pacific and north atlantic and sedimentary cycle patterns in marine successions exposed onland in the mediterranean in this paper we present a review of the progress subsequently made in establishing a late neogene astronomical polarity time scale a p ts in the mediterranean region major steps forward are 1 the evaluation of the initial time scale using high resolution climatic proxy records different astronomical solutions and the additional influence of obliquity on sedimentary cycle patterns 2 the extension of the a p ts into the middle miocene i e back to about 12 3ma 3 the closure of the messinian gap in the a p ts 4 the incorporation of the continental record and 5 the intercalibration of astronomical and radioisotopic time

messinian erosional and salinity crises view from the provence basin gulf of lions western mediterranean abstract though the late miocene messinian salinity crisis has been intensely researched along the circum mediterranean basins few studies have focused on the central part of the mediterranean basin and especially the pre salt deposits to improve our knowledge of the messinian events it is imperative to better understand this domain in this study we provide a more complete understanding of this central domain in the provence basin we were able to recognize a thick marine detrital series up to 1000 m derived from the messinian subaerial erosion which is partly prolongated in the distal part by b a thick unit of deep marine deposits up to 800 m prior to the evaporites c a thick presumed alternation of detritals and evaporites 1500 m below the mobile halite and d a two step transgression at the end of the messinian spatially we document the eroded shelf to the deep basin and from the western to the eastern parts of the gulf of lions and temporally we extend the interpretations from the early deposition of detritic sediments to the final sea level rise the results provide a new basis for discussion not only for the development of the messinian salinity crisis but also for the reconstruction of the subsidence history of the provence basin

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

distribution patterns of live planktic foraminifers as related to regional hydrography and productive systems of the mediterranean sea abstract distribution patterns of live planktic foraminifers are examined at two times of the year late summer and late winter through horizontal plankton towing along a nw se transect across the west and east mediterranean basins and in the alboran sea french oceanographic cruises vicomed i ii and iii respectively foraminiferal production is significantly different in the two sampling periods and across the west and east mediterranean foraminiferal density is higher in winter than summer e g in the western basin 3700 specimens 1000 m3 in winter against 200 600 specimens 1000 m3 in summer the production averaged for the two sampling sets is higher in the western basin than in the eastern one however in late summer peaks of maximal production are observed in the central mediterranean strait of sicily and ionian basin 1000 to 2000 specimens 1000 m3 where the assemblages are dominated by globigerinoides ruber rosea and g ruber alba in the mediterranean sea frontal regions and semipermanent eddies which are essentially controlled by regional hydrography represent a significant portion of the regional production they also elicit a higher diversity of species their influence is observed in summer as well as in winter at the end of summer the rather shallow mixed layer hosts spinose symbiont bearing species such as g ruber alba g ruber rosea o universa and g trilobus at that season in the western basin the nutrient content of the mixed layer is generally low and the surface layer is rapidly nutrient depleted summer foraminiferal production remains low at the surface with respect to the winter production in the eastern basin late summer and autumn correspond to the biological spring summer foraminiferal production in surface waters is higher than in winter but standing crops are lower than in the western basin for the same species at the same period in summer however frontal structures and eddies are generally better developed than in winter in some particular cases frontal boundaries in the western basin eddies south of cyprus nutrients from intermediate layers can be upwelled through isopycnal or diapycnal mixing to the photic zone and allow for secondary blooms in the western basin these blooms favour the development of grazers at depth globorotalia truncatulinoides g inflata south of cyprus in the eastern basin oligotrophic conditions promote the development of heterotrophic organisms and predatory foraminifers have higher standing stocks g ruber alba g ruber rosea in winter the break down of the thermocline combined with deep turbulent mixing in the northwestern basin and the deepening of the mixed layer in the alboran sea and along the north african coast result in increased phytoplankton biomass and favour reproduction and proliferation of species such as g truncatulinoides or g inflata our observations indicate that the geographic and depth distribution of live foraminiferal species cannot be entirely explained by the general temperature and salinity differences among the different mediterranean basins but that they are strongly related to regional hydrographic patterns hydrography controls the seasonality and depth of the turbulent mixing which differ between the western and the eastern basins the depth of the mixed layer and its seasonal stratification and the strength of the pycnocline nutrient supply and primary production are mostly regulated by these dynamics one may therefore expect that the species assemblages on the sea floor and in deep sea cores will also correlate to the various hydrographic parameters of the overlying water masses

the messinian post evaporitic deposits of the gafares area almeria nijar basin se spain a new view of the lago mare facies abstract the exceptional exposures of the evaporitic and post evaporitic messinian deposits in the gafares area ne almeria nijar basin se spain make it possible to elucidate those processes affecting this region during the critical period of the messinian salinity crisis the contact between the pre evaporitic and the evaporitic units is an erosional unconformity the transition from the evaporitic to the post evaporitic units is gradual since the gypsum beds of the evaporitic unit thin upward and the siliciclastic interbeds concomitantly thicken thus passing gradually to the overlaying post evaporitic unit the presence of globorotalia miotumida group in the last pelitic intercalation of the evaporitic unit as well as throughout the post evaporitic one indicates a messinian age the post evaporitic unit consists of a variety of sediments formed in continental and marine settings continental facies are characterised by fluvial channel filled conglomerates and alluvial plain sands and silts marine sediments are represented by silty marls with foraminifers a river dominated delta developed in the transitional zone at the nw edge of the gafares area localised fan delta deposits coming from the ese also occur in the southeastern part of the study area microbial carbonates locally colonised the fan delta conglomerates during the deposition of the lower half of the post evaporitic unit sedimentation took place in a sheltered embayment with restricted water circulation and relatively isolated from the mediterranean sea by an e w trending sill located at the south of the study area in this palaeogeographic context freshwater influx from the delta exerted a certain influence on the distribution of microorganisms thus brackish settings developed close to the river outflows that were occupied by caspibrackish ostracod assemblages the presence of gastropods of the family cerithiidae as well as fishes attributable to the genus aphanius organisms that preferentially inhabit sheltered lagoons is consistent with these settings beyond the freshwater influx foraminifers dominated the microfossil assemblages in the upper half of the post evaporitic unit microfossil assemblages dominated by planktonic forms are consistently found thus revealing a better connection of the semi enclosed gafares area with the marine domain this is related to the deepening of the sill due to a progressive rise of the sea level the continental and brackish deposits zorreras like facies have been equated with the lago mare facies which were supposed to spread throughout the whole mediterranean at the end of the messinian nevertheless in the gafares area these deposits change laterally to and interbed with marine deposits this stratigraphic architecture and facies relationship has two important implications on the one hand marine waters at the latest messinian occupied at least the western mediterranean predating the long claimed early pliocene deluge on the other hand the continental brackish lago mare facies were spatially restricted as a consequence neither the presence of the caspibrackish ostracods nor the continental brackish facies can be plausibly taken to support the hypothesis that widespread lago mare facies occupied the whole mediterranean synchronously at the end of the messinian therefore this type of facies is expected to be found albeit with varying degrees of development in marginal basins at different times but not throughout the mediterranean

40ar 39ar dating of the pre evaporitic messinian marine sequences of the melilla basin morocco a proposal for some biosedimentary events as isochrons around the alboran sea in the mediterranean region the melilla basin ne morocco represents a key area that recorded biosedimentary events and environmental changes relative to the pre evaporitic messinian times 40ar 39ar dating of volcanic tuffs interbedded all along the melilla messinian shelf carbonates and coeval basin deposits has been performed in order to date accurately three main pre evaporitic biosedimentary events the prograding bioclastic deposition and the oligospecific prograding porites coral reef buildings with coeval halimeda blooms both within the platform and the diatomite deposition basinward the new age data allow a precise chronological framework to be established for the pre evaporitic sequence of melilla basin demonstrating that diatomitic deposits are coeval with both prograding bioclastic and reefal units the prograding bioclastic carbonate unit related to boreal influences in coeval basinal diatomites began at least at 6 73 0 02 ma and ended at 6 46 0 03 ma the oligospecific prograding porites coral reefs and halimeda beds and coeval warm water diatomites began at least at 6 46 0 03 ma previous 40ar 39ar ages indicate that they ended prior to 6 0 0 1 ma both biosedimentological similarities and chronological accordance within several platforms and adjacent basins all around the alboran sea show that these main bioevents dated in melilla are synchronous over the alboran realm this accurate time scale for these pre evaporitic biosedimentary events 6 9 6 0 ma is in accordance with the most recent work on the latter period corresponding to the messinian salinity crisis

incidence of obliquity and precession forced milankovitch cycles in the western mediterranean early messinian sedimentation in the sorbas basin almeria southern spain spectral analysis of the messinian abad marls in the cariatiz section sorbas basin south eastern spain reveals three relevant orders of cyclicity the most significant cycle is in the lowest frequency average thickness of 365 cm 4 5 cycles in the section it is recorded in the composition of planktic foraminiferal assemblages indicative of surface water temperature planktic and benthic stable isotope signals and carbonate proportions the planktic assemblages isotope values and carbonate proportions also record a middle frequency cycle with an average of 177 cm 9 10 cycles in the section the highest frequency cycle average of 132 cm 12 13 cycles in the section is mainly reflected in siliciclastic and calcite proportions age constraints and cycle patterns suggest that the lowest frequency cycle was forced by orbital obliquity whereas the two higher frequency ones are related to precession obliquity seems to have controlled major changes in surface water temperature in the sorbas basin during the early messinian surface water temperature was also affected by precession with changes in weathering and run off spectral analysis has also been applied to vertical shifts of reef facies throughout the progradation of the cariatiz reef this reef is coeval with the cariatiz section vertical shifts of reef talus breccias point to the existence of 4 5 major cycles of sea level change whereas 7 9 higher frequency cycles are reflected in the repeated occurrence of lowstand non reefal deposits correlation with the cycles observed at the cariatiz section suggests that obliquity forced glacio eustatic sea level oscillations in the western mediterranean during the late miocene

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

the tortonian salinity crisis of the eastern betics spain the late miocene depositional history of the lorca and fortuna basins both occupying an internal position in the eastern betics of spain is marked by a regressive sequence from open marine marls via diatomites and evaporites to continental sediments based on facies similarities these evaporites have often been correlated to the well known mediterranean evaporites of the messinian salinity crisis although this correlation was never substantiated by reliable chronological data in this paper we present an integrated stratigraphy of this regressive sequence which shows that the evaporites of the lorca and fortuna basins are entirely of late tortonian age and as such have no relation with the messinian salinity crisis the main phase of basin restriction resulting in deposition of diatomites and evaporites took place at 7 8 ma while the last marine deposits massive evaporites of the lorca basin are dated at 7 6 ma consequently this tortonian salinity crisis of the eastern betics had a duration of approximately 200 kyr while continental deposition prevailed throughout the entire messinian as also revealed by the fossil mammal record the tortonian salinity crisis of the eastern betics is obviously related to a local phase of basin restriction caused by uplift of the metamorphic complexes at the basin margins probably in concert with strike slip activity along sw ne trending fault systems the development of a submarine sill is of crucial importance for the increase in salinity because it allows marine waters to continuously enter the basin at the surface while it restricts or prevents the outflow of dense saline waters at depth furthermore we show that evaporite and diatomite cyclicity in these restricted basins is predominantly related to precession controlled circum mediterranean climate changes and that glacio eustatic sea level changes only play a minor role it is remarkable that the lithological sequence of the tortonian salinity crisis mimics in many aspects that of the messinian salinity crisis this suggests that the diatomaceous facies is an essential part of the lithological sequence associated with basin restriction fl 2000 elsevier science b v all rights reserved

origin and implications of orbital induced sedimentary cyclicity in pliocene well logs of the western mediterranean abstract the climatic origin of astronomically induced sedimentary cycles in the mediterranean and adjacent areas during the late neogene and quaternary remains puzzling as cycles have been linked to concomitant but seasonally opposite changes in african summer monsoon precipitation eastern mediterranean sapropels and atlantic regulated winter precipitation carbonate cycles on the atlantic side of the mediterranean particularly little is known about the cyclic sedimentation on orbital time scales in the western mediterranean with the prime exception of the messinian sapropels from the sorbas basin southern spain here we show that regular alternations in pliocene downhole logs from the industrial drill site muchamiel 1 located along the balearic promontory in the western mediterranean are related to eccentricity bundles and to obliquity and precession cycles basic meter scale alternations we establish an astronomically based age model for the interval between 5 33 and 2 8 ma by first correlating cycle bundles to eccentricity and then the basic dominantly precession related cycles to the 65 n summer insolation of la2004 the striking bed to bed similarities between the muchamiel 1 well logs and other records from both the atlantic margin and the central mediterranean suggest that the same climatic forcing was responsible for the formation of carbonate cycles across the western mediterranean and adjacent atlantic we conclude that formation of alternating carbonate rich carbonate poor beds was controlled by western mediterranean cyclogenetic mechanisms as well as by peri mediterranean precipitation associated with changes in the north atlantic system nas these findings highlight the importance of peri mediterranean precipitation on the sedimentary cyclicity by dictating terrigenous clay supply and potentially on the hydrology of the basin by providing additional freshwater required for sapropel formation consequently cyclic sedimentation in the mediterranean results from the combined effect of precipitation changes driven by i the north african monsoon ii the atlantic system and iii intrabasinal mediterranean atmospheric dynamics

correlation of late miocene to early pliocene sequences between the mediterranean and north atlantic ocean drilling program odp site 982 in the north atlantic contains a complete latest miocene to early pliocene section that was tuned to the astronomical timescale by correlating the record of gamma ray attenuation gra bulk density to summer insolation at 65 n and the benthic 18o signal to orbital obliquity for the interval from 4 6 to 7 5 ma the astronomical tuning of the site 982 record permits a direct bed to bed correlation to the cyclostratigraphy of messinian sections in the mediterranean krijgsman et al 1999a 2001 the benthic 18o signal at site 982 records a latest miocene glacial period that lasted from 6 26 to 5 50 ma and consisted of 18 glacial to interglacial oscillations that were controlled by the 41 kyr cycle of obliquity although the intensification of glaciation at 6 26 ma may have contributed to the restriction of the mediterranean it preceded the depositional onset of the lower evaporite unit at 5 96 ma by some 300 kyr the transition from stage tg12 to tg11 at 5 5 ma marks the end of the latest miocene glacial period and precedes the miocene pliocene boundary by 170 kyr although benthic 18o values are relatively low and 18o of bulk carbonate reaches a minimum at the miocene pliocene boundary at 5 33 ma there is no single event that would indicate deglaciation and sea level rise as the cause of the reflooding of the mediterranean we conclude that glacioeustatic changes alone were not responsible for either the start or end of evaporite deposition during the messinian suggesting that tectonic or local climate changes in the mediterranean region were the dominant cause s

the abad composite se spain a messinian reference section for the mediterranean and the apts a high resolution integrated stratigraphy is presented for the abad marls of the sorbas and nijar basins in se spain preevaporitic messinian of the western mediterranean detailed cyclostratigraphic and biostratigraphic analyses of partially overlapping subsections were needed to overcome stratigraphic problems in particular encountered at the complex transition from the lower to the upper abad the resulting abad composite section contains a continuous stratigraphic record from the tortonian messinian boundary up to the transition to the messinian evaporites of the yesares member all together 18 calcareous plankton events were recognized which were shown to be synchronous throughout the mediterranean by means of detailed bed to bed cyclostratigraphic correlations the magnetostratigraphy allowed the identification of the four magnetic reversals of chron c3an in the upper abad details in the sedimentary cycle patterns allowed the abad composite to be astronomically calibrated this calibration to the 658n summer insolation curve of solution la90 1 1 yielded astronomical ages for all sedimentary cycles calcareous plankton bioevents ash layers and paleomagnetic reversals up to now the abad composite is the only astronomically well calibrated section that provided a reliable cyclostratigraphy magnetostratigraphy and calcareous plankton biostratigraphy as such it will serve as a reference section both for the pre evaporite messinian in the mediterranean as well as for the messinian interval in the astronomical polarity time scale q 2001 elsevier science b v all rights reserved

internal structure of segment reefs halimeda algal mounds in the mediterranean miocene halimeda reefs in the upper miocene strata 6 ma of the sorbas basin southeastern spain shed light on the internal structure of more extensive but less accessible holocene counterparts and challenge conventional reef concepts coarse discoid segments released by halimeda during life or immediately after death dominate the lenslike mounds their chaotic loose appearance disguises the reefal nature of the mounds segments accumulating at or very close to sites of growth were quickly stabilized by microbial and cement crusts that bound them into distinctive rigid gravel fabrics this early lithification generated relief but inhibited off mound export of sediment although large blocks detached locally and moved downslope encrustation of parautochthonous halimeda gravel created a unique reef type segment reefs

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

magnetostratigraphic biostratigraphic and stable isotope stratigraphy of an upper miocene drill core from the sale briqueterie northwestern morocco a high resolution chronology for the messinian stage we report a high resolution stable isotope carbonate magnetostratigraphic and biostratigraphic record from a 175 m drill core from the sale briqueterie which is part of the bou regreg section in northwestern morocco the sale drill core spans the interval from paleomagnetic chron c4n partim to c3r earliest gilbert which represents the time leading up to and including the isolation and desiccation of the mediterranean i e the messinian salinity crisis during chrons c3an and c3ar 6 935 to 5 894 ma the isotope and carbonate signals display quasi periodic variations with estimated periods of 40 and 100 kyr respectively we interpret the 40 kyr 18o variations as reflecting changes in global ice volume caused by obliquity induced changes 41 kyr in solar insolation in polar regions the 100 kyr carbonate variations probably represent long term modulation of the amplitude of the precessional cycle 21 kyr which is not resolved by our sampling frequency the cyclic nature of the oxygen isotope signal permits us to extend the isotope nomenclature of shackleton et al 1994a from stage tg24 in chron c3r earliest gilbert to stage c3ar 18o 18 at the base of chron c3ar 6 935 ma a major change in paleoceanographic conditions is recorded across the tortonian messinian boundary which we correlate to chron c3bn at 7 04 ma benthic foraminiferal 18o values increased by an average of 0 4 in two steps at 7 17 ma and 6 8 ma and 13c values decreased by 0 7 0 8 between 7 1 and 6 8 ma representing the late miocene carbon shift the first step in 18o values coincides with an inferred reversal in deep water circulation through the rifian corridor and the second correlates with the base of the tripoli formation and onset of crisis conditions in the mediterranean we suggest that the increase in 18o values represents at least in part an increase in global ice volume that lowered sea level and contributed to the establishment of a negative water budget in the mediterranean average 18o values remained high throughout most of chrons c3ar and c3an reaching maximum 18o values during isotope stages tg20 and 22 in chron c3r earliest gilbert the glacio eustatic falls associated with these events may have resulted in the complete isolation of the mediterranean from the world ocean shackleton et al 1994a following stage tg12 in the sale record there exists a trend toward progressively lower 18o values that may represent a series of marine transgressions that eventually reflooded the mediterranean and ended the salinity crisis

a reconstruction of late miocene mediterranean circulation patterns using benthic foraminifera abstract extensive research on the late miocene mediterranean has solved a number of questions concerning the development of the area but questions remain on for instance the mediterranean water circulation patterns knowledge of preferably quantitative oxygen contents of water masses could be of help to reconstruct paleo circulation and understand how this contributed to the development of the mediterranean messinian salinity crisis msc bottom water oxygenation is usually estimated qualitatively or semi quantitatively at best from abundances of infaunal benthic foraminifera from stable carbon isotope data or redox sensitive elements we present data from six mediterranean land sections and one section located at the atlantic side of the rifian corridor as an atlantic reference location we introduce a semi quantitative reconstruction of oxygen levels at the sediment water interface employing a simple index that operates on a scale from 1 low oxygen to 5 normal to high oxygen using this method we present a tentative reconstruction of the mediterranean water circulation in the period preceding the continuous development towards the msc which started at 7 17 ma we found that during the late miocene an anti estuarine circulation was likely quite comparable to the modern pattern deep water formation appears to have existed in the central northeastern part of the basin around 7 2 ma constriction of the rif corridor morocco led to restricted exchange of mediterranean and atlantic water masses a reduction of the deep circulation and decreasing bottom water ventilation deep water formation weakened and the mediterranean hydrography changed thoroughly eventually contributing to the development of the msc

three hundred eighty thousand year long stable isotope and faunal records from the red sea influence of global sea level change on hydrography stable isotope and faunal records from the central red sea show high amplitude oscillations for the past 380 000 years positive 18o anomalies indicate periods of significant salt buildup during periods of lowered sea level when water mass exchange with the arabian sea was reduced due to a reduced geometry of the bab el mandeb strait salinities as high as 53 and 55 are inferred from pteropod and benthic foraminifera 18o respectively for the last glacial maximum during this period all planktonic foraminifera vanished from this part of the red sea environmental conditions improved rapidly after 13 ka as salinities decreased due to rising sea level the foraminiferal fauna started to reappear and was fully reestablished between 9 ka and 8 ka spectral analysis of the planktonic 18o record documents highest variance in the orbital eccentricity obliquity and precession bands indicating a dominant influence of climatically driven sea level change on environmental conditions in the red sea variance in the precession band is enhanced compared to the global mean marine climate record specmap suggesting an additional influence of the indian monsoon system on red sea climates

toward a high resolution chronology for latest miocene paleoceanographic events it is now widely accepted that expansion of continental glaciers is one manifestation of profound paleoenvironmental change in latest miocene time the oxygen isotopic record in deep sea cores is inferred to document brief pulses in glaciation based on covariance of 18o in benthic and planktonic foraminifera which probably lowered latest miocene sea level by a minimum of 60 m additional evidence of glacial activity in the oxygen isotope record is obscured by the small signal amplitude before further details of paleoenvironmental change can be investigated it is essential to have a high resolution stratigraphy and chronology this has not been achieved previously because most studies of the latest miocene have had a sampling interval greater than the duration of events they seek to resolve a high resolution stable isotope record from the north atlantic deep sea drilling project dsdp 552 is correlated with a second record from the southwest pacific dsdp 588 each core has magnetostratigraphy but there are two possible interpretations of magnetic results in the atlantic core by assuming that brief events of 18o enrichment and 13c depletion in each core are synchronous it is possible to assign the most likely age model to the atlantic core results of this exercise indicate that two 18o maxima occurred at 4 8 and 5 2 ma if these events reflect continental glaciation and if sea level was lowered enough to contribute to isolation and desiccation of the mediterranean then the miocene pliocene boundary must be close to 4 8 ma in age because messinian deposits are latest miocene in age this interpretation is consistent with biostratigraphy at dsdp 552 magnetostratigraphy biostratigraphy and isotope stratigraphy at a site commonly referred to because of its proximity to the mediterranean dsdp 397 northwest african continental margin and recent work on land in the mediterranean region

glacial holocene salinity changes in the mediterranean sea hydrographic and depositional effects oxygen isotope changes as recorded by pleistocene foraminifera from open ocean sediments are primarily a function of changes in the isotopic composition of the global seawater reservoir caused by ice volume changes with a secondary temperature component1 oxygen isotope records from marginal basins such as the gulf of mexico2 the mediterranean sea3 5 and the red sea6 also exhibit the global signal but are far more complicated owing to the strong overprint of local climate conditions in particular glacial interglacial changes in continental aridity and river runoff produce significant salinity changes in these semi enclosed basins using available oxygen isotope records we estimate that glacial 18 000 yr bp salinities in the eastern and western mediterranean sea were 2 7 and 1 2 higher respectively than at present these elevated glacial salinities played an important part in preconditioning the eastern mediterranean for the eventual accumulation of organic carbon rich sediments sapropels at the end of deglaciation

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

paleoenvironmental conditions preceding the messinian salinity crisis in the central mediterranean integrated data from the upper miocene trave section italy abstract integrated data of calcareous plankton and benthic foraminifers from the pre evaporitic interval of trave section central italy allowed the reconstruction of surface and bottom water conditions in the central mediterranean during the interval from 7 61 to 6 33 ma preceding the messinian salinity crisis our data point out a three step paleoenvironmental evolution during the first stage 7 61 7 02 ma benthic foraminiferal assemblages depict stable well oxygenated and ventilated bottom water conditions while the surface water records variable temperature and high nutrient conditions probably associated with strong seasonality the second stage 7 02 6 70 ma points to unfavourable bottom water condition triggered by deep sea stagnation this is witnessed by a significant decrease in oxygen concentration and biotic diversity and by the presence of stress tolerant taxa a general warming of the surface water and a strongly stratified water column characterized by an expanded mixed layer are also recorded from 6 70 ma onwards third stage a prominent change to more restricted low oxygenated hypersaline conditions at the sea floor is testified by the total disappearance of deep dwelling planktonic foraminifers and the increasing abundance of stress tolerant species calcareous plankton reflects high instability of the surface water in terms of nutrients temperature and salinity during this stage the environmental deterioration reaches intermediate depths in the water column the initial change toward a step wise isolation of the central mediterranean bottom waters is probably related to a general warming responsible for a first slowing down of the vertical circulation favouring stratification of surface and intermediate waters and stagnation of bottom waters this warming is related to the restricted connection between the mediterranean sea and the atlantic ocean which occurred since 7 146 ma in the trave section the isolation of bottom waters most likely occurred at the same time as in other mediterranean sections however due to the presence of a hiatus it cannot be excluded that it occurred with a delay of 100 kyr probably related to the shallower paleodepth of the basin

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

late miocene mediterranean desiccation topography and significance of the salinity crisis erosion surface on land in southeast spain comment one of the most striking aspects of the mediterranean messinian salinity crisis as observed in landbased sections is the basin wide synchronicity in facies change krijgsman et al 1999a the messinian succession of the caltanisetta basin on sicily serves as the classical standard for these facies changes which can also be recognised elsewhere in the mediterranean i e on cyprus crete northern italy and southern spain it starts with an alternation of open marine marls and sapropels passes via diatomites into evaporitic limestones gypsum and halite of the lower evaporites of marine origin and following an erosional unconformity ends with the upper evaporites and associated fresh to brackish water deposits of the lago mare that are essentially of non marine origin and contain a caspi brackish ostracode fauna the erosional unconformity between the lower and upper evaporites is assumed to reflect the phase of most extreme sea level drawdown in the mediterranean that caused significant erosion and localised channel entrenchment on the continental shelves and slopes

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

western versus eastern mediterranean paleoceanographic response to astronomical forcing a high resolution microplankton study of precession controlled sedimentary cycles during the messinian abstract planktic foraminifera and stable isotopes were analyzed in samples from four precession controlled sedimentary cycles from southeastern spain and the island of gavdos greece to reconstruct the paleobiologic and paleoceanographic response of the western and eastern mediterranean to astronomically driven climate variability during the messinian although the lithological succession in the western mediterranean cycles sapropel homogeneous marl diatomite homogeneous marl is different from that in the eastern mediterranean sapropel diatomite homogeneous marl the pelagic biological succession is similar four stages were recognized in both environments characterized by the dominance of warm oligotrophic foraminifera stage 1 neogloboquadrinids and globorotaliids stage 2 globigerina bulloides stage 3 and globigerinita glutinata stage 4 the first stage occurs during deposition of the upper part of the sapropels in spain and the sapropels and part of the diatomites on gavdos this stage is inferred to relate to high summer insolation and strong surface water stratification with winter temperatures not high enough to allow eutrophic foraminifera growth stage 2 occurs during the deposition of the lower homogeneous marls in spain and the middle upper part of the diatomites in greece most likely indicating stratification with colder winter temperatures and a nutricline above the euphotic layer the end of surface water stratification is indicated during stage 3 by the replacement of the neogloboquadrinids by g bulloides which occurs at the base of the diatomites in spain and near the top of the diatomites in greece we link this event to the appearance of dryer climates in the mediterranean at times of relatively low summer insolation in the northern hemisphere which would result in higher surface salinities deep water convection and deep water ventilation stage 4 defined by the dominance of g glutinata and low concentrations of planktic foraminifera appears linked to the base of the sapropels both in the western and eastern mediterranean the onset of sapropel deposition occurred at a time of relatively high surface water salinities as suggested by the heavy 18o in orbulina universa and prior to the development of surface water stratification evident in the subsequent increase in warm oligotrophic foraminifera gavdos diatomites were deposited under anoxic conditions whereas sorbas diatomites were formed in an oxygenated environment the difference between western and eastern mediterranean diatomites would be due to differences in hydrographic conditions between the two studied settings

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

correlations and sequence stratigraphic model for messinian carbonate platforms of the western and central mediterranean distance correlations of late tortonian messinian littoral carbonate complexes are proposed from the study of eight platforms in the western and central mediterranean correlations are based on the identification of two major biological sedimentary cycles and of two index surfaces surface a is a maximum flooding surface during cycle 1 at around 6 7 ma surface b is a regional marine planation surface at around 5 95 ma at the base of cycle 2 terminal carbonate complex a general sedimentary model is proposed for the 7 5 6 ma time span the boundary between cycles 1 and 2 is coincident with the onset of the messinian salinity crisis and appears to be related to major environmental paleo oceanographic changes in the mediterranean rather than to a major sea level drop or to climatic change

the late messinian salinity crisis and late miocene tectonism interaction and consequences on the physiography and post rift evolution of the gulf of lions margin the interpretation of rhone maritime seismic profiles and the accurate mapping of all the structural features affecting the miocene cover made it possible for us to develop herein a new structural model for the top of the eroded miocene of the gulf of lions platform late miocene extensional faults exerted a considerable structural control on the messinian erosion in particular mapping of transfer zones has shown that these structures controlled retrogressive erosion of the platform this late miocene extension could have been caused by gravity driven destabilization of the platform associated with base level lowering at the onset of the messinian salinity crisis

foraminiferal record of environmental changes messinian of the los yesos area sorbas basin se spain the late messinian of the sorbas basin betic cordillera se spain has been sampled to estimate 1 the paleoenvironmental changes recorded by the benthic foraminifers in pre evaporitic and evaporitic units and 2 the impact of the messinian salinity crisis on the foraminiferal biodiversity in the pre evaporitic unit foraminifers indicate a circalittoral to bathyal environments and show significant changes in bottom water oxygenation simultaneously the occurrences of epiphytic damaged foraminifers and the blocks of porites point out the presence of plant substrates and coral reefs on the infralittoral zone the overlying evaporitic unit is characterized by four subaqeous selenitic gypsum layers and three marine fossiliferous intercalations each episode of gypsum deposition ends with a desiccation event each fossiliferous intercalations traduce a rapid reflooding of the basin by marine waters corresponding to infralittoral to upper bathyal environments with normal marine conditions during the evaporitic period the ecological conditions in the water column were intermittently favorable to the development of marine organisms and moreover the marginal basins of the betic cordillera were not continuously desiccated during the messinian the low percentage of extinct species 5 at the messinian pliocene boundary and the occurrences of benthic foraminifers in the evaporitic unit indicate that the infralittoral to upper bathyal environments have not been completely modified and or barren during the messinian salinity crisis i e the messinian salinity crisis is not associated with a biological crisis

the messinian salinity crisis in the adriatic foredeep evolution of the largest evaporitic marginal basin in the mediterranean abstract the recent release of a large number of subsurface geological data by the italian minister of economic development including boreholes and seismic profiles provided the occasion for a new assessment of the deposits associated with the messinian salinity crisis msc in the adriatic foreland basin system and a new integration with the outcropping successions of the apennines in particular the study of the messinian evaporites allowed to reconstruct a new detailed palaeogeographic and palaeobathymetric framework for all the stages of the crisis we identified the largest evaporitic marginal basin ever described for the mediterranean hosting the precipitation of the primary shallow water gypsum deposits plg primary lower gypsum during the first stage of the crisis during the second and third stages of the crisis the plg basin underwent uplift and erosion and the evaporite accumulation moved to the deeper part of the basin and was characterized by the deposition of the resedimented lower gypsum unit including clastic evaporites recycling the plg ones primary halite and terrigenous deposits the distribution of the different evaporitic facies was the basis for an improved reconstruction of the upper miocene tectonic evolution of the apennines thrust belt our results show a clear separation between shallower depocenters located in the wedge top and in the adriatic foreland basins and characterized by msc stage 1 plg deposition and deeper water ones located in the adriatic foredeep and close to the calabrian arc where msc stage 2 terrigenous and gypsum bearing clastic deposits and primary halite accumulated

new insights on the sorbas basin se spain the onshore reference of the messinian salinity crisis the sorbas basin is the land reference of the messinian salinity crisis msc that affected the mediterranean sea in the latest miocene its stratigraphy has been re visited using calcareous nannofossils and planktonic foraminifers which provide a reliable biostratigraphic frame and lead to particularly specify the relationships between the sorbas and zorreras members with yesares evaporites the evaporites overlie a shallowing upward sequence ending with the deposition of the reef unit and terminal carbonate complex tcc on the periphery of the basin the reefal carbonates of the tcc are overlain by clastic deposits that are foreset beds of post msc gilbert type fan deltas developed on the northern edge of the basin these sedimentary structures are separated from reefal carbonates and the reef unit by the messinian erosional surface mes the various facies of the sorbas member have been correlated with the bottomset beds of the gilbert type fan deltas despite some differences in palaeobathymetry in the southeastern periphery of the basin the mes separates the sorbas member from the yesares gypsums in the central part of the basin a hiatus characterizes the contact between these members the zorreras member postdates the msc and entirely belongs to zanclean its white lago mare layers are lagoonal deposits the fauna of which is confirmed to result from mediterranean paratethys high sea level exchange after the post msc marine reflooding of the mediterranean basin this study allows to re assert the two step scenario of the msc clauzon et al 1996 with the following events at 5 971 5 600 ma minor sea level fall resulting in the desiccation of this peripheral basin with secondary fluctuations at 5 600 5 460 ma significant subaerial erosion or lack of sedimentation caused by the almost complete desiccation of the mediterranean sea instantaneous marine reflooding accepted at 5 460 ma followed by continuing sea level rise

astrochronology for the messinian sorbas basin se spain and orbital precessional forcing for evaporite cyclicity the sorbas basin of se spain contains one of the most complete sedimentary successions of the mediterranean reflecting the increasing salinity during the messinian salinity crisis a detailed cyclostratigraphic study of these successions allows a correlation of the sedimentary cycle patterns to astronomical target curves here we present an astrochronological framework for the messinian of the central part of the sorbas basin this framework will form a solid basis for high resolution correlations to the marginal carbonate facies and to the central mediterranean area the early messinian abad member contains 55 precession induced sedimentary cycles marked by homogeneous marl opalrich bed alternations in the lower abad and by homogeneous marl sapropel alternations in the upper abad astronomical tuning results in an age of 5 96 ma for the transition to the yesares evaporites and thus for the onset of the messinian salinity crisis the marl sapropel cycles of the upper abad are replaced by gypsum sapropel cycles 14 in the yesares member indicating that the evaporite cyclicity is related to precession controlled oscillations in circum mediterranean climate as well as a consequence gypsum beds correspond to precession maxima insolation minima and relatively dry climate sapropelitic marls to precession minima insolation maxima and relatively wet climate an alternative glacio eustatic obliquity control for evaporite cyclicity can be excluded because the number of sedimentary cycles with a reversed polarity is too high sedimentation during the abad yesares and the overlying coastal sequences of the sorbas member took place in a continuously marine environment indicating that marine conditions in the sorbas basin prevailed at least until 5 60 5 54 ma according to our scenario deposition of the yesares and sorbas member took place synchronously with deposition of the lower evaporites in the central mediterranean finally the continental zorreras member consists of 8 sedimentary cycles of alternating reddish silts dry climate and yellowish sands wet climate which correlates very well with the upper evaporites and lago mare facies of the mediterranean q 2001 elsevier science b v all rights reserved

messinian events new constraints from sedimentological investigations and new 40ar 39ar ages in the melilla nador basin morocco abstract new 40ar 39ar ages obtained both from within a platform and from the adjacent basin allow through the extension of a previous argon dataset the establishment of a chronological framework for the messinian carbonate complex of melilla morocco in the platform prograding bioclastic deposits began around 6 87 0 02 ma whereas the youngest preserved deposits are 5 77 0 04 ma old the southern part of the basin was uplifted and emergent prior to 6 23 0 03 ma the tortonian messinian and the messinian pliocene boundaries have not yet been identified in the melilla region durations of the prograding bioclastic deposits ca 410 ka the prograding porites reefs ca 360 ka and the preserved part of the terminal carbonate complex tcc ca 330 ka can be estimated sedimentological and geochronological investigations do not indicate any major subaerial unconformity nor any major time gap if a major sea level fall did exist during messinian times it developed after 5 77 0 04 ma chronological correlations show that the onset of the sorbas gypsum deposition southern spain considered as the marker of the messinian salinity crisis onset is contemporaneous with aggrading porites reef building of the terminal carbonate complex of melilla a major paleoceanographic change in the marginal areas of the mediterranean with the cessation of upwelling systems could be partly coeval with the onset of the messinian salinity crisis

extension of the astronomically calibrated polarity time scale to the miocene pliocene boundary the early pleistocene to late pliocene astronomically calibrated time scale of shackleton et al 1 and hilgen 2 is extended to the miocene pliocene boundary this is done by correlating the detailed record of caco3 cycles in the trubi and the lower part of the overlying narbone formation rossello composite section sicily to the astronomical record using 1 inferred phase relations between these caco3 cycles and the corresponding orbital cycles of precession and eccentricity and 2 calibration points provided by the previously established astronomical calibration of sapropelitic layers which occur in the topmost part of the caco3 record 2 this correlation allows all small scale caco3 cycles in the rossello composite section to be coded after the correlative precession peak and to be dated astronomically with an accuracy of 1 ky in combination with the available high resolution magnetostratigraphy it further allows the construction of an astronomically calibrated geomagnetic polarity time scale for the major part of the gilbert and gauss chrons this new time scale gives ages for the reversal boundaries of the kaena 3 04 3 11 ma and mammoth 3 22 3 33 ma the gilbert gauss chron boundary 3 58 ma and the reversal boundaries of the cochiti 4 18 4 29 ma nunivak 4 48 4 62 ma sidufjall 4 80 4 89 ma and thvera 4 98 5 23 ma these ages are significantly older than the ages given by conventional time scales age discrepancies gradually increase with increasing age the age of 5 32 ma for the miocene pliocene boundary as defined by the base of the trubi on sicily is almost 0 5 m y 9 5 older than the presently accepted age of 4 86 ma 3 these considerable discrepancies with the conventional time scale can either be explained by an consistent error in the decay constants used in k ar radiometric dating or more likely by diffusional loss of radiogenic argon

post deformational annealing of calcite rocks abstract the evolution of microstructure and crystallographic preferred orientation cpo during post deformational annealing was studied on three calcite rock types differing in purity and grain size carrara marble 98 calcite mean grain size of 115 m solnhofen limestone 96 5 m and synthetic calcite aggregates 99 7 m samples were first deformed in torsion at 727 c at a shear strain rate of 3 10 4 s 1 to a shear strain of 5 and subsequently heat treated at 727 c for various durations between 0 and 24 h microstructures and cpos were analysed by optical microscopy image analysis and electron backscatter diffraction ebsd all rock types deformed in the dislocation creep field at the same applied conditions but their microstructures and cpos after deformation and after annealing differed depending on starting grain size and material composition in carrara marble and in the synthetic calcite aggregate a strong cpo developed during deformation accompanied by dynamic recrystallisation with significant changes in grain size during annealing widespread grain growth and subtle changes of cpo occurred and equilibrated foam microstructures were approached after long annealing times the cpo is the only feature in annealed samples indicating an earlier deformation phase although it is not always identical to the cpo formed during deformation in the more impure solnhofen limestone secondary phases on grain boundaries suppressed grain boundary mobility and prevented both the formation of a recrystallisation cpo during deformation and grain size modification during deformation and annealing

climatic and hydrologic variability in the northern mediterranean across the onset of the messinian salinity crisis abstract the youngest and one of the largest saline deposits of earth history formed in the mediterranean during the messinian salinity crisis msc 5 97 5 33 ma late miocene when global climate was experiencing a trend of cooling and aridification however recent paleoclimate reconstructions indicate strong climate gradients across the mediterranean basin and the persistence of humid conditions in the northern mediterranean during the earliest phase of the msc to characterize climatic and hydrologic variability across the onset of the msc we studied inorganic geochemical proxies comprising si ti and zr element distributions and organic geochemical proxies such as sedimentary plant wax contents and their carbon 13cn alk and hydrogen 2 n alk stable isotope compositions in deep water 200 m alternating shale and marl deposits of the piedmont basin govone section nw italy our results suggest that deposition was controlled by precession driven climate fluctuations before and after the onset of the msc with shales deposited under moister conditions lower element al ratios and 2 n alk values and marls when drier conditions prevailed higher element al ratios and 2 n alk values the observed 2 n alk pattern further suggests changes in the relative contributions of the sources of moisture for precipitation at precession minima shales were deposited and moisture was mainly sourced from the north atlantic as reflected by lower 2 n alk values at precession maxima marls were deposited and higher 2 n alk values point to a probably western mediterranean source of moisture the decrease of element al ratios as well as the coeval increase of plant wax abundances after the onset of the msc indicate enhanced humidity and increased net precipitation over the northern mediterranean these changes coincided with a restriction of the atlantic mediterranean gateways and resulted from an enhanced contribution of deuterium enriched moisture sourced from seawater evaporation in the mediterranean evidenced by an increase of 2 n alk values

regional climate and glacial control on high resolution oxygen isotope records from ain el beida latest miocene northwest morocco a cyclostratigraphic analysis in the depth and time domain 1 high resolution benthic and planktonic stable oxygen isotope records are presented for the upper miocene ain el beida aeb section in northwestern morocco and reveal the clear imprint of the climatic precession obliquity and eccentricity cycles in the interval between 6 5 and 5 5 ma the 18o depth series were transformed into time series using astronomical tuning of the sedimentary color cycles to the 65 n summer insolation curve of the la93 solution with present day values for tidal dissipation and dynamical ellipticity spectral analysis and band pass filtering show that the ratios of the astronomically related spectral peaks are not consistent in the depth and time domain the inconsistencies are mainly due to variations in sedimentation rate that are positively correlated with precession amplitude i e modulated by eccentricity in addition they result from a long term trend in sedimentation rate a simple model of nonlinear response of the sedimentation rate to the eccentricity modulation of precession was used to simulate the observed shifts in the relative position of the spectral peaks in the depth domain cross spectral analysis was carried out on the 18o time series and a combined eccentricity tilt obliquity and precession etp curve the precession controlled 18o signal varies in phase with etp partly as a result of the tuning procedure while the obliquity related signal reveals a small lag of 2 3 kyr relative to obliquity this lag is slightly reduced at the time of the messinian salinity crisis msc and increases to 5 6 kyr if the tidal dissipation term in the astronomical solution is reduced to half its present day value the obliquity related lag is most likely associated with the slow buildup of ice caps whereas the precession signal is interpreted as to dominantly reflect regional climate changes comparable to those associated with mediterranean sapropels finally the benthic 18o record is compared with open ocean records and discussed in terms of an astronomically tuned oxygen isotope stratigraphic framework

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 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 late messinian lago mare event and the zanclean reflooding in the mediterranean sea new insights from the cuevas del almanzora section vera basin south eastern spain abstract the return to normal marine conditions in the mediterranean sea after the end of the messinian salinity crisis msc that led to the deposition of thick evaporitic succession followed by settlement of brackish to freshwater conditions of the lago mare is still subject to extensive debate between two opposite scenarios one scenario implies an abrupt reflooding through the gibraltar gateway of the mediterranean sea previously disconnected from the world ocean and partly desiccated the second scenario postulates that the mediterranean sea kept a high water level throughout the messinian salinity crisis and was connected continuously to the atlantic ocean and to the paratethys the stratigraphic record of the classical cuevas del almanzora section vera basin is of a crucial importance as the vera basin is located on the eastern margin of the alboran sea close to the gibraltar gateway where atlantic waters reflooded the mediterranean sea after the msc the present new study completes previous investigations pierre et al 2006 and is mostly focused on detailed sedimentological observations analysis of ostracod and foraminifer assemblages and on stable isotopes study of three species of planktonic foraminifers globigerina bulloides globigerinoides obliquus s l and sphaeroidinellopsis spp from the lower pliocene deposits biostratigraphical correlations with the reference deep sea section from odp site 975 balearic basin and the onshore succession of eraclea minoa sicily provide an accurate chronostratigraphy and paleoclimatic reconstruction during the zanclean during the late messinian the vera basin was characterized by very unstable lacustrine to brackish environments with significant water depth variations and the deposits display evidences of subaerial exposure the ostracod content is dominated by loxocorniculina djafarovi and cyprideis gr agrigentina associated to reworked planktonic foraminifera from older sediments the messinian zanclean contact is well marked by a clear erosional surface that grades laterally into a megabreccia with reworked gypsum blocks and to the large incision of the palomares canyon in the offshore domain the marine reflooding occurred abruptly with a sea level rise by more than 250 m an important value for a marginal basin in this western part of the mediterranean sea the marine invasion began with the onset of the lowermost biozone mpl 1 at the base of the zanclean the fluctuations of the planktonic foraminifer assemblages and of their stable isotopes allowed to identify five lithological cycles forced by milankovitch precession periodicity as well as paleoclimatic variations through the lower part of the zanclean thus these new data allow us to reaffirm that the messinian zanclean boundary corresponds to a major change characterized by an instantaneous restoration of marine conditions at the onset of the pliocene related to the abrupt re flooding of the mediterranean sea from the atlantic ocean

sedimentological and paleoenvironmental scenario before during and after the messinian salinity crisis the san miguel de salinas composite section western mediterranean abstract a composite stratigraphic section ranging from the messinian to the pliocene recording the most important phases of the messinian salinity crisis is represented in the san miguel de salinas area bajo segura basin se spain detailed magnetostratigraphic and facies analyses and foraminifer and nannoplankton assemblage studies were carried out integration of the results has allowed the characterization of the pre evaporitic synthem messinian i syn evaporitic synthem messinian ii and post evaporitic phases synthem pliocene from a paleoenvironmental and chronostratigraphic standpoint the pre evaporitic phase is late messinian and records a shallowing upward trend the syn evaporitic phase took place in chron c3r and is characterized by laminated marls with intercalated selenitic gypsum beds and sandstones variations in foraminifer and nannoplankton assemblages together with episodic gypsum precipitation record major changes in water salinity in a stressed marine environment the pre and syn evaporitic phases are separated by the intra messinian unconformity represented by an erosional surface related with a sea level fall after the evaporitic phase a sea level fall generates the end messinian unconformity whose strongly erosional nature is evidenced by the deeply carved paleovalley of san miguel de salinas the post evaporitic phase begins in the earliest pliocene and records the re establishment of normal marine conditions in the basin since the san miguel de salinas composite section can be considered as a benchmark for the study of the evolution of marginal mediterranean basins during the messinian salinity crisis the detailed characterization of these different phases is of great importance in understanding this event

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

glacio eustatic sea level control on red sea salinity previous studies of the red sea demonstrated that glacial surface and bottom water salinities in the basin were significantly higher than at present the very low abundance of planktonic foraminifera the so called aplanktonic zone during the last glacial indicates that surface water conditions approached or exceeded the tolerance limits of this plankton group1 2 glacial sediments are also characterized by high concentrations of magnesian calcite3 4 dolomite3 inorganically precipitated aragonite4 5 and benthic foraminifera typical of hypersaline environments3 6 additional evidence from oxygen isotope records of planktonic2 7 and benthic foraminifera8 9 as well as pteropods2 demonstrate that glacial interglacial contrasts in the red sea have an amplitude much larger than typically observed in open ocean records here we use both oxygen isotope data and a fractional overmixing model to estimate the impact of the most recent 18 000 yr bp pleistocene glacio eustatic sea level lowering on red sea salinity we estimate that during the last glacial maximum surface salinities in the central red sea were more than 10 0 higher than at present deep water salinities were also higher during the last glaciation and remained unusually high through deglaciation the combination of very high bottom salinities and the onset of pluvial conditions during deglaciation in the red sea region prevented ventilation of red sea bottom waters and resulted in the accumulation of organic rich sediments

the coral reef of nijar messinian uppermost miocene almeria province s e spain abstract the nijar reef is a thoroughly exposed and representative example of the messinian coral reefs outcropping along the periphery of the western mediterranean facies patterns in the nijar reef complex are presented in this paper as a generalized guide or model for the study of other messinian reefs messinian paleogeography of this area was characterized by an archipelago whose islands are present day sierras at the beginning of the messinian and before development of the reefs marine terrigenous sediments marginal terrigenous complex were deposited on an irregular erosion surface on the metamorphic basement the reef complex developed as a belt fringing the positive areas islands when terrigenous deposition decreased the reef complex consists of 1 reef core constructed by a framework of vertical branching colonies of porites coated by laminated micrite probably submarine cements which form pinnacles as well as thickets and 2 fore reef made of sloping beds of broken skeletons and debris the fore reef is subdivided into i reef talus slope ii proximal slope and iii distal slope the reef talus forms massive strata with dips of 20 30 and abundant pebble to boulder size slumped blocks of reef core and coral breccia the proximal slope shows dips of 10 20 of well bedded thick strata with internal parallel layering of granule to sand size skeletal calcarenites the distal slope is made of predominant bioturbated skeletal calcisiltites and fine grained calcarenites with ngles lower than 10 the distal slope grades into the basinal pelagic marls of the nijar plains the original reef morphology is well preserved in present day topography with relicts of pinnacles reef valleys and slopes messinian volcanic highlands located to seaward complicated the local paleogeography with atoll like features reef growth was concomitant with a gradual fall of sea level and occurred before the messinian gypsum was deposited on top of the basinal marls in what is now the plains area the reef complex is partially truncated by a major erosion surface and it is overlain by oolitic shoals and stromatolites of the so called terminal carbonate complex the terminal complex is interpreted as an upslope equivalent in age to the messinian upper evaporite and it implies a new cycle of sea level rise

the messinian early pliocene stratigraphic record in the southern bajo segura basin betic cordillera spain implications for the mediterranean salinity crisis financial aid was provided by research projects bte2003 05047 cgl2005 06224 bte cgl2007 65832 bte mec and gv04b 629 generalitat valenciana and the paleoenvironmental changes group ua

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

after the deluge mediterranean stagnation and sapropel formation in an east mediterranean marine core the upper sapropel begins soon after the start of a global event a very heavy precipitation which occurred in the equatorial latitudes during the late glacial early holocene this heavy precipitation in africa channelled by the nile river across 35 of latitude produced a low salinity surface layer in the east mediterranean in this confined basin with high bottom salinity the steep salinity gradient stratified the water column the stagnant bottom waters triggered the sapropel formation cretaceous sapropels in the tropical oceans may result from the same chain of events in warm humid climates with contrasting wet and dry seasonal rhythm

on the origin of upper miocene sapropelites a case study from the faneromeni section crete greece for the first time results of an integrated geochemical and micropalaeontological study of upper miocene sapropelites in a land based section in the mediterranean are presented three sapropelites and adjacent homogeneous intervals in the cretan faneromeni section have been investigated in detail the chemical and foraminiferal characteristics were found to be markedly similar to those of plio pleistocene sapropelites as the physiography and climate of the late miocene mediterranean were not fundamentally different from those of today our preferred model for late miocene sapropelite formation is similar to the one recently developed for plio pleistocene sapropelites increased seasonality and freshwater input during northern hemisphere summer insolation maxima triggered high export production and oxygen consumption rates which in combination with a concomitant decrease in deep water formation rate resulted in the observed high organic matter content of the sapropelites

high frequency rhythmicity in a mixed siliciclastic carbonate shelf late miocene guadix basin spain a model of interplay between climatic oscillations subsidence and sediment dispersal abstract rhythmites in pelagic sediments can include information on paleoclimate and with orbital cycles this paper documents and interprets an unusual rhythmic succession from a cool water shallow marine shelf that includes features of mediterranean type ramps and open ocean type ramps in the subsiding southwestern margin of the guadix basin southern spain betic cordillera during the late tortonian a 640 m thick succession was deposited over a short period 7 8 7 2 ma this succession contains 30 sedimentary packages or rhythmites each defined by two facies associations a mixed cross stratified siliciclastic skeletal sandstone and a homogeneous marl rich in planktonic foraminifera sandstones ranging in thickness from 3 m to 20 m contain coralline algae bivalves bryozoans benthic foraminifera echinoids and brachiopods typical temperate water shelf biofacies these units exhibit cross strata sets up to four meters high interpreted to have been produced by strong unidirectional currents the marly deposits range in thickness from 2 to 17 m and contain an association of cold water planktonic foraminifera as well as thin sandstone layers that exhibit normal grading corresponding to typical incomplete bouma sequences or a lower division with planar lamination and an upper division of very fine to fine grained sandstone with hummocky and swaly cross stratification on the basis of the sedimentary structures the sandstone layers are interpreted as sporadic turbidity flows and storm ebb surge deposits on the basis of the sedimentary structures the hydrodynamic conditions during deposition of the mixed siliciclastic carbonate interval were high energy based on sedimentary and biogenic features of the rhythmites and their temporal durations ca 20 ka rhythmicity is interpreted to reflect alternating cool wet and cold dry climate episodes driven by precession orbital cycles this occurrence of alternating mixed carbonate siliciclastic sedimentation and pelagic sediments represents a unique occurrence in the geologic record

orbitally controlled oscillations in planktic communities and cyclic changes in western mediterranean hydrography during the messinian we use quantitative analyses of the planktic foraminiferal assemblages and stable isotope analyses of the sorbas section in the western mediterranean to reconstruct the cyclical changes in surface and deep water hydrographic conditions during the late miocene prior to the messinian salinity crisis oscillations in winter and summer temperatures linked to cyclical fluctuations in the hydrographic conditions and nutrient availability were the main mechanisms driving the cyclical changes in the planktic foraminiferal assemblages during the messinian the winter intensification and southward expansion of the northern cool and dry winds during precession maxima lowered sea surface temperatures below 14 15 c favoring water convection and the upward mixing of nutrients with the consequent increase in the proportion of cold eutrophic water foraminifera the low summer temperatures below 24 c inhibited the growth of warm oligotrophic water foraminifera as occurs today in the mediterranean by contrast at times of precession minima the low influence of the high latitude air masses caused winter temperatures to remain relatively high which combined with the lower surface salinities led to the formation of a permanent pycnocline winter conditions prevented the growth of cold eutrophic water foraminifera while high summer temperatures and the formation of a permanent pycnocline stimulated the growth of warm oligotrophic water foraminifera the prevalence of stable water stratification during winter due to the large density gradient between the surface and intermediate waters prevented deep water formation and slowed down the rates of oxygen supply to the bottom resulting in the formation of the sapropels a sharp decrease in 13c of benthic and planktic foraminifera that occurred between 6 8 and 6 7 myr is related to an increase in the residence time of mediterranean waters because similar changes have been observed in other regions of the mediterranean we conclude that this change records a significant reduction in the atlantic mediterranean water exchange at that time mediterranean climatic amplification increased throughout the messinian as the atlantic mediterranean water exchange was progressively more limited and oscillations in the ratio of planktic benthic foraminifera and of warm oligotrophic cold eutrophic species are good records of this increasing amplification which culminated at 5 95 myr with the deposition of gypsum pelitic layers that mark the onset of the messinian salinity crisis

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

african monsoons an immediate climate response to orbital insolation the croll milankovitch astronomical theory of climate1 3 has received strong support from the evidence of a linear climatic forcing by obliquity and precession although nonlinearity had to be assumed for eccentricity4 5 moreover interglacials have appeared to be controlled by the orbital insolation6 although a phase shift of 6 000 5 000 yr is seen between an astronomical climate index and terrestrial climate indicators dominated by the northern ice sheet dynamics climate proxy data of low latitudes are less directly dependent on the ice sheets here it is shown that during the past 464 000 yr african monsoons signalled by the east mediterranean sapropels were heaviest always and only when a northern summer monsoon index computed from the orbital variation of insolation reached maximum values this occurred during all the interglacials but also twice during glacial periods thus tropical aridity is not the single climatic pattern of glacial periods an immediate terrestrial climate response to orbital variations of insolation is established

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

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

fluvial evaporitic and shallow marine facies architecture depositional evolution and cyclicity in the sivas basin lower to middle miocene central turkey abstract lower to middle miocene rocks in the karayun region of the sivas basin are represented by the agilkaya and egribucak formations forming a 4 km thick continuous section each formation is subdivided into three members representing similar lithofacies the lower members are made up of fluvial sheet sandstone and red mudstone that migrated laterally on a flood basin within a semi arid fan system the middle members are composed of bedded to massive gypsum and red green mudstone of a coastal and or continental sabkha environment they are intercalated with lagoonal dolomitic limestone and bituminous shale in the agilkaya formation and fluvial red pink sandstone red mudstone in the egribucak formation the upper members are made up of shallow marine fossiliferous mudstone and sandy limestone rapid vertical and horizontal facies changes in both formations reflect the locally subsiding nature of this molassic basin the overall section can be also subdivided into three orders of fining upward cycles type i cycles correspond to the agilkaya and egribucak formations each around 2 km thick and indicate two long term transgressive phases controlled by tectono eustatic factors type ii cycles 140 m thick on average are formed by alternations of fluvial sheet sandstone and red mudstone capped by up to 50 m thick red flood basin mudstone a 400 ka period milankovitch cyclicity related to astronomical climatic fluctuations is suggested as a governing mechanism although subsidence cannot be excluded the existence of laterally persistent fluvial sheet sandstone overlain by red mudstone that forms fining upward type iii cycles 10 m thick on average is attributed to changes in subsidence rate rhythmic alternations between gypsum beds and red green mudstone and or dolomitic limestone and bituminous shale observed in the middle members might be related to minor periodical climatic changes rather than to tectonics

a sediment nutrient oxygen feedback responsible for productivity variations in late miocene sapropel sequences of the western mediterranean abstract cyclic sediments observed throughout the mediterranean during the late miocene have been related to precessional forcing of ocean stratification individual couplets typically 2 m thick sequences of sapropels and diatom rich marls can be reliably traced from western spain to crete and were formed in restricted marginal basins micropaleontological evidence indicates paradoxically that the organic carbon rich sapropels were formed under low productivity conditions marked by surface water stratification and deep anoxia whereas the diatom rich marls were formed under high productivity conditions marked by upwelling here we present geochemical evidence mainly from detailed phosphorus determinations and paleo redox proxies indicating that a sediment nutrient oxygen feedback herein dubbed the sno effect is in part responsible for driving the observed productivity variations during stratification anoxic conditions in these basins cause the release of the limiting nutrient phosphorus from reducible oxide phases in the sediments basin stagnation causes the buildup of phosphorus below the photic zone subsequent overturn driven by precessionally driven winds injects phosphorus rich bottom waters into the photic zone the biotic response to this overturn is high productivity in marls directly overlying the sapropels culminating in diatom mat formation exhaustion of the stored excess phosphorus results in lower productivity marls which grade back into sapropels due to lower wind stresses and the return of stagnant basin conditions these findings indicate that the sno effect may in part be responsible for precessional scale productivity variations observed in parts of the mediterranean and perhaps present in other restricted ocean basins like the miocene monterey formation and the modern santa barbara basin

evolution of depositional environments after the end of messinian salinity crisis in nijar basin se betic cordillera abstract the messinian succession is exceptionally well preserved in the intramontane sedimentary basin of nijar in the internal betic cordillera se spain gypsum olistostromes and large slabs of the azagador member are unconformably overlain by the latest messinian sediments of the feos formation these deposits which are studied in detail in the rambla los feos outcrop basinal area are characterized by a sedimentary cyclicity and two lithostratigraphic units can be distinguished 1 a lower one that mainly consists of calcarenitic intervals with laminated pelites and limestone beds 2 an upper unit showing a cyclic alternation of fluvial fan deposits and lacustrine marls that corresponds to the lago mare episode the sedimentary succession records very precisely the strongly fluctuating environmental conditions during the upper messinian as well as the paleomorphological and paleogeographical changes that are likely related to late miocene and pliocene tectonic uplift of the sierra cabrera betic basement the dominant fossil content present throughout the upper unit in the lacustrine white marls of the feos formation is represented by ostracods of the loxocorniculina djafarovi fa an assemblage of non marine aquatic communities which lived in brackish water bodies lago mare fauna extant ostracod faunas similar to those documented in the messinian fossil record and characterised by cyprideis tyrrhenocythere loxoconchids and leptocytherids occur in hypohaline water bodies in a salinity range of approximately 5 15 mesohaline water however the number of species of parathetian affinity is low as observed in other perimediterranean areas i e apennines the marine fauna association foraminifera present at levels is thought to be partly reworked even though a marine influence at the end of the lago mare stage is not excluded

integrating outcrop data and forward computer modelling to unravel the development of a messinian carbonate platform in se spain sorbas basin geological mapping definition of facies distributions and reconstruction of platform interior growth geometries of the messinian cariatiz carbonate platform sorbas basin south spain were performed to evaluate the controlling factors in platform growth and to test a 3 d computer simulation program for the simulation with the program repro five platform related facies were modelled 1 the reef crest facies by the numerical solution of a fisher equation 2 the lagoonal facies by a function of water depth dependent carbonate production 3 the proximal and middle slope facies breccia and block facies calcarenite facies by a subroutine simulating gravity driven particle export from the reef crest 4 a distal slope and 5 a basinal facies by a pelagic rain function development of a fan delta conglomeratic system is simulated by using a siliciclastic point source and gravity driven particle redistribution a best fit between the observed platform growth geometries and modelling results is achieved by assuming that high frequency sea level changes superimposed onto a longer term sea level fall controlled platform growth for the modelling a relative sea level curve was reconstructed which is based on a deep sea benthic foraminiferal stable oxygen isotope record at odp site 926 with a 45 m eustatic sea level fall and a tectonic uplift component of 20 m the consistency of 3 d simulation results is corroborated by the coral growth rates provided by the fisher equation subroutine these rates of 28 mm year1 compare well to the coral growth rates in recent fringing reefs we propose that during the early stage of platform evolution the high frequency fluctuations were obliquity modulated precessional cycles whereas precessional cycles control later stages of platform growth repro provides a separate visualization of the different facies bodies as a function of time and space showing the intrinsic pattern of facies distribution in the platform this is the result of a combination of platform growth and syndepositional subaerial erosion for example only the youngest stages of reef framework facies in the development of the cariatiz carbonate platform are preserved

precession related sapropelites of the messinian sorbas basin south spain paleoenvironmental significance abstract the sorbas basin southern spain is a narrow and elongated basin located in the betic corridor that formed the northern connection between the atlantic and the paleomediterranean during the late miocene in the centre of the basin about 120 m of well preserved cyclic marine sediments crop out ranging in age from 7 2 to 6 myr these cycles make up the abad member and are an excellent example of precession control over sedimentation in the upper part of the sequence upper abad member the cycles include organic rich laminated brown marls sapropelites alternating with homogeneous marls displaying diatomite layers the om rich laminated marls are the westernmost sapropelites of the mediterranean this paper is a geochemical mineralogical sedimentological and micropaleontological analysis of three cycles with sapropelites the data enable us to distinguish two main climatic scenarios the climate which dominated each of these scenarios regulated the sedimentology and the physico chemistry of the water column resulting in the sapropelite homogeneous marl cyclic alternations the sapropelites developed during a climate characterised by a long period of temperate and humid conditions that occur at times of precession minima these climatic conditions changed progressively to a subarid and drier weather during which homogeneous sediments were deposited the changes between these scenarios were gradual as expected from precession dynamics our data suggest that the change from the subarid to the humid climate transition from homogeneous marls to laminated sapropelites took place at a faster rate or at least was recorded more rapidly by the sediments than the transition from the humid interval to the sub arid period

the messinian of the nijar basin se spain sedimentation depositional environments and paleogeographic evolution abstract the reconstruction of the depositional events related to the messinian salinity crisis msc of the mediterranean is generally hampered by an incomplete stratal record in the circum mediterranean basins the sediments of the northern part of the nijar basin however provide an excellent and continuous record of late messinian sediments because features of severe erosion are lacking especially the successions of the deeper part of the basin had sufficient accommodation space to warrant ongoing deposition and may thus serve as a testing ground for existing hypotheses regarding the msc conformable contacts with the overlying pliocene and good correlation possibilities with the adjacent astronomically dated messinian of the sorbas basin provide the necessary age constraints the main body of evaporites in the nijar basin yesares formation has been affected by local dissolution and erosion prior to deposition of the latest messinian lago mare facies pelitic float breccias show textures indicating flowage and or mass transport and include slumped and slided stratal packets due to foundering of the mixed evaporitic clastic margin increased runoff of meteoric waters probably played an important role as these packet slides are perfectly sealed by the hyposaline lago mare strata field observations show that marginal sediments commonly classified as the terminal carbonate complex tcc are a lateral equivalent of the basinal yesares evaporites the latest messinian deposits feos formation are characterized by a sedimentary cyclicity related to fluctuating base levels consisting of chalky marly laminitic strata alternating with continental coarser clastic intervals despite considerable w e facies changes and indications for discrete tectonic events a persistent sequential pattern of eight lago mare cycles is present which are interpreted as precession controlled variations in regional climate instead of one major desiccation event in the latest messinian the repeatedly fluctuating water levels of the lago mare episode may have been the cause of the widespread vigorous erosion and canyon cutting in the lower evaporites abrupt non erosional contacts with the normal marine pliocene take place above the continental interval of the last lago mare cycle indicating that flooding took place during a period of lowered water levels the paleogeographic configuration of the nijar sorbas and vera basins has changed considerably during the messinian separation of the formerly interconnected basins is thought to have started in the late yesares times by tectonic uplift of the basement complexes in the latest messinian of the nijar basin two different coarse clastic supply areas can be distinguished which point to the partial emergence of the sierra cabrera and the cabo de gata block and activity of the sierra alhamilla and carboneras faults concerning the overall regional tectonic activity tectonics were probably also instrumental for the restoration of the atlantic gateway in the basal pliocene

the miocene pliocene boundary and the messinian salinity crisis in the easternmost mediterranean insights from the hatay graben southern turkey accepted manuscript version published version at http dx doi org 10 1016 j sedgeo 2015 11 012 license in accordance with the journal s policy cc by nc nd

shallow lacustrine carbonate microfacies document orbitally paced lake level history in the miocene teruel basin north east spain results are presented of a detailed carbonate petrographic study of an upper miocene lacustrine mixed carbonate siliciclastic succession in the teruel basin spain with the aim of constraining lake level variability at different stratigraphic scales regular alternations of red to green mudstone and lacustrine limestone termed the basic cycle reflect lake level variations at the metre scale in an earlier study the basic cycle was shown to be controlled by the climatic precession cycle petrographic analysis made it possible to distinguish two main carbonate microfacies groups characteristic of very shallow transient and shallow permanent lake environments respectively in addition to the basic cyclicity the microfacies analysis reveals lake level variations on a larger scale as a consequence the astronomical forcing hypothesis of the cyclicity in the cascante section is explored further a climate modelling study of orbital extremes indicates that high lake levels could relate to enhanced net winter precipitation and runoff during precession minima consistent with mediterranean geological data using this phase relationship an astronomical tuning of the cycles is established starting from astronomical ages of magnetic reversal boundaries subsequently successive basic cycles are correlated to precession minima the tuning reveals an identical number of basic cycles in the cascante section as precession related sapropel cycles in the deep marine succession at monte dei corvi italy corroborating the precessional control of the basic cycles at cascante lake level highstands in the large scale cycle identified by the microfacies analysis relate to maxima in both the ca 100 and 405kyr eccentricity cycles again consistent with mediterranean geological data subtraction of the identified astronomically related lake level variations from the palaeoenvironmental record at cascante indicates a shift to deeper and more permanent lacustrine environments in the upper half of the section the cause of this shift remains unclear but it may be linked to tectonics non astronomical climate long period astronomical cycles or autogenic processes 2008 the authors journal compilation 2008 international association of sedimentologists

precessional variability of 87 sr 86 sr in the late miocene sorbas basin an interdisciplinary study of drivers of interbasin exchange we present the first subprecessional record of seawater 87sr 86sr isotope ratios for a marginal mediterranean subbasin the sediments contained in this interval three precessional cycles between 6 60 and 6 55 ma are important because they record conditions during the transition to the messinian salinity crisis msc 5 97 to 5 33 ma an event for which many details are still poorly understood the record derived from planktic foraminifera of the late miocene sorbas basin se spain shows brief excursions with precessional cyclicity to 87sr 86sr ratios higher than coeval ocean 87sr 86sr the hydrologic conditions required to generate the observed record are investigated using box modeling constrained using a new paleodepth estimate 150 to 250 m based on benthic foraminiferal assemblages the box model results highlight the role of climate driven interbasin density contrast as a significant driver of or impediment to exchange the results are particularly significant in the context of the msc where 87sr 86sr excursions have been interpreted purely as a consequence of physical restriction to replicate the observed temporal patterns of lithological variations and 87sr 86sr isotope excursions the sorbas basin box must have a mainly positive hydrologic budget in contrast with the mediterranean s negative budget during the late miocene this result has implications for the assumption of synchronous deposition of specific sedimentary layers sapropels between marginal and open mediterranean settings at subprecessional resolution a net positive hydrologic budget in marginal mediterranean subbasins may reconcile observations of freshwater inclusions in gypsum deposits

surface water dynamics and phytoplankton communities during deposition of cyclic late messinian sapropel sequences in the western mediterranean abstract distinctive precession scale sapropel marl sequences of late messinian age are found in several outcrops bordering the western mediterranean to examine the roles of stratification and productivity in driving this cyclic sedimentation we performed a high resolution analysis of calcareous nannofossil assemblages through four orbital sequences composed of sapropel marl diatomite marl from the sorbas basin in southern spain this effort also involved a detailed comparison between calcareous nannofossil abundances and other micropaleontological sedimentological and geochemical proxies to further understand the behaviour of some taxa for this period fluctuations in the depth and gradient of the pycnocline and the distribution and remobilization of nutrients seem to be the main factors controlling the calcareous nannoplankton assemblages with temperature of secondary importance in the sapropels the warm oligotrophic genus sphenolithus and discoaster are abundant especially significant is the progressive increase towards the top of discoaster pentaradiatus indicator of severe oligotrophic deep pycnocline conditions at the top of the sapropels peaks in reticulofenestra rotaria are interpreted here as the result of an increase of surface water temperatures although decreasing salinity may also play a role small reticulofenestra 5 m are more frequent in diatomites even considering conditions of extreme mixing and eutrophication occurred in the basin umbilicosphaera jafari peaks just after diatomites replacing small reticulofenestra probably as a response to an increase in salinity and or nutrient limitation species such as coccolithus pelagicus and helicosphaera carteri are abundant at the top of the diatomites and in the overlying marls indicating relatively mesotrophic and cool water conditions this succession shows similar characteristics in the four studied cycles allowing us to interpret surface water dynamics in this region on orbital time scales the top of the sapropel represents a warm low salinity and well stratified episode under a situation of maximum insolation a well developed pycnocline and oligotrophic conditions moderate production of calcareous phytoplankton coinciding with anoxic conditions at the bottom enhance the preservation of organic matter and consequently generate a sapropel diatomites are deposited under a situation of unstable pycnocline that produce an increase in productivity in surface waters diatoms significantly deplete limiting nutrients and consequently calcareous nannofossils start to be dominant again in the water column as result of a progressive stabilization of the pycnocline

mediterranean quaternary sapropels an immediate response of the african monsoon to variation of insolation abstract in the subsurface of the east mediterranean sea eleven discrete basin wide organic rich black sapropels were deposited during the last 465 000 years they are dated by oxygen isotopic chronostratigraphy the most recent sapropel has been shown to be the consequence of heavy nile river summer floods due to increased monsoonal summer precipitation over ethiopia and not of scandinavian ice sheet meltwater influx into the east mediterranean sea as was previously believed while most sapropels were deposited during interglacials two thick sapropels formed during glacial periods as shown by their position in the oxygen isotopic stratigraphy and by their pollen record in core rc9 181 the new evidence presented here is that the sapropel sequence in this core including the two glacial sapropels correlates on a one to one basis with the highest values of an index of insolation on top of the atmosphere the concept of this index derives from an analysis of the african monsoon process the index variation is computed for the last 465 000 years from the caloric northern summer insolation in the tropical latitudes controlled by variations of the earth s orbital parameters it is conjectured that this index might be linked through the climate system to the monsoonal precipitation which in africa produces the nile river summer flood

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

review and new aspects concerning the formation of eastern mediterranean sapropels abstract in this paper it is proposed that the formation of eastern mediterranean sapropels occurred in an anti estuarine type of circulation which was to some degree weakened relative to the present in response to reduction of the eastern mediterranean excess of evaporation over freshwater input this reduction of excess evaporation would have been imposed by intensifications of 1 the indian ocean summer sw monsoon influencing the eastern mediterranean via increased nile discharge and 2 the system of mediterranean depressions an element of the westerly atlantic system causing increased precipitation and decreased evaporation both the indian ocean summer monsoon and the westerly atlantic system would be intensified in response to the occurrence of distinct minima in the cycle of precession it is demonstrated that reduced excess evaporation whether or not coinciding with global phases of deglaciation would lead to reduction of surface water salinities in the eastern mediterranean causing isolation of previously formed high salinity cooler deep water thus mixing was severely reduced possibly even restricted to eddy diffusion with only occasional convective events that because of the existing density gradient hardly ever would reach the deepest parts of the basin the consequently diminished oxygen advection down from a few hundred meters in the water column favoured preservation of the sinking organic matter this would however suffice only to enable the formation of sapropels with low organic carbon contents the high organic carbon contents observed in various sapropels are argued to reflect superimposed increases of export production the described scenario accounts for previously reported 1 increases of organic carbon content with increasing depth of deposition within individual sapropels and 2 asymmetrical sequences of sapropel deposition characterized by gradual build up and rather abrupt ending it is furthermore in agreement with 3 isotopic and faunal reconstructions of the history of exchange transports through both the strait of sicily and the strait of gibraltar and 4 faunal and floral reflections of the presence or absence of a distinct deep chlorophyll maximum with its associated increases in export production indicating the presence or absence of a shallow pycnocline within the euphotic layer moreover the described scenario 5 is in no way conflicting with the reports of sapropels in the western mediterranean and 6 seems to be endorsed by occasionally intercalated intervals suggestive of somewhat improved oxygenation amidst anoxic benthic desert levels a situation that has been observed in a few quaternary and pliocene sapropels