anaerobic oxidation of methane in hypersaline messinian environments revealed by 13c depleted molecular fossils abstract the messinian sequence of evaporitic deposits in italy includes authigenic carbonates that have been suggested to derive from the microbial degradation of organic compounds but the biogeochemical mechanisms that led to their formation remained unknown to unravel these mechanisms 13 c depleted carbonate rocks including native sulphur bearing limestone calcare solfifero from two locations in sicily and bedded limestone from the northern apennines have been studied their 13 c values as low as 49 reflect incorporation of carbon derived from the oxidation of methane which was previously suggested to have been linked to bacterial sulphate reduction molecular fossils extracted from the limestones reveal that methane was indeed oxidized in an anaerobic process by archaea and sulphate reducing bacteria the observed biomarker patterns resemble those of methane seep carbonates which form as a consequence of the anaerobic oxidation of methane aom aom specific 13 c depleted archaeal biomarkers such as pmi 13 c 101 to 75 as well as compounds derived from sulphate reducing bacteria iso and anteiso fatty acids 13 c as low as 85 were identified in the messinian carbonates although the biomarker results clearly point to aom the compound inventory also revealed distinct differences to patterns found at marine methane seeps for example sn 3 hydroxyarchaeol is in some samples the only hydroxyarchaeol present something usually not found at seeps archaeol is less depleted in 13 c than pmi at most sites 13 c 55 to 30 pointing to the co occurrence of methanogenic or halophilic archaea with archaea involved in aom 1 the presence of calcite pseudomorphs after lenticular gypsum 2 18 o enrichment in carbonates and 3 the biomarkers o phytanyl o sesterterpanyl glycerolether extended archaeol tetrahymanol and possibly phytanylglycerol monoethers as well as non isoprenoidal macrocyclic glycerol diethers confirm that carbonate formation took place under evaporitic conditions aom has previously been shown to be inhibited in some brine pools on the modern seafloor our observations however demonstrate that aom functions in hypersaline environments as well

the end of the messinian salinity crisis in the western mediterranean insights from the carbonate platforms of south eastern spain abstract how the messinian salinity crisis msc ended is still a matter of intense debate the terminal carbonate complex tcc is a late messinian carbonate platform system that recorded western mediterranean hydrological changes from the final stages of evaporite deposition till the advent of lago mare fresh to brackish water conditions at the very end of messinian times a multidisciplinary study has been carried out in three localities in south eastern spain to reconstruct the history of tcc platforms and elucidate their significance in the msc overall this study provides evidence that the tcc formed following a regional 4th order water level rise and fall concomitant with an opening restriction trend it can be subdivided into four 5th order depositional sequences ds1 to ds4 recording two phases 1 from ds1 to ds3 a tide dominated ooidic to oobioclastic system with stenohaline faunas developed as a result of a 70 m water level rise during this period the tcc developed in a shallow sea with close to normal marine salinity 2 in depositional sequence 4 a microbialite dominated platform system developed this is indicative of a significant environmental change and is attributed to a 30 to 40 m water level fall in the basins under study these restricted conditions were coeval with intense evaporite deformation and brine recycling the syn sedimentary deformation of evaporites had a major impact on platform architecture and carbonate production affecting the messinian series throughout south eastern spain at the end of the tcc history at that time the tcc developed in a lake with fluctuating brackish to hypersaline water these findings suggest a temporary restoration of marine conditions in the western mediterranean marginal basins due to atlantic water influxes prompted by a global sea level rise around 5 6 ma whether marine conditions extended to the entire western mediterranean still needs to be investigated

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

structural styles and regional tectonic setting of the gela nappe and frontal part of the maghrebian thrust belt in sicily the gela nappe of south central sicily provides an example of a curved segment of an orogenic front that can be examined both onshore and offshore for deformational style and amount of shortening synorogenic sediments allow the deformation to be dated two distinct structural styles are observed in the gela nappe the central salient part of the nappe caltanissetta basin consists of a single thrust sheet containing a train of continuously tightening folds and the reentrant margins of the nappe sciacca and monte judica consist of a stack of several thrust sheets these different structural styles correspond to the pretectonic mesozoic stratigraphy of the foreland plate carbonate platforms exist on the adventure bank and hyblean plateau ahead of sciacca and monte judica respectively while the caltanissetta basin region appears to have accumulated basinal clay facies where the resistant carbonate stratigraphy provides a buttress to the propagation of the thrust front deformation is taken up by imbrication on steep ramps through the carbonates generating a relatively thick orogenic wedge in the basinal setting where no strong rheology exists the low angle of friction on the clay detachment levels requires the growing thrust wedge to be much thinner with a very low foreland dip hence the thrust front propagates much farther forward into the basin than it does in the adjacent platformal areas producing a nonlinear thrust front in the basinal region accretion of foreland material to the nappe by imbrication was only prominent during the messinian when subaerial exposure prevented low friction transport of the nappe across the highest levels of the stratigraphy a steady thickening of the nappe by internal folding suggests an increase in friction along the basal detachment possibly due to progressive compaction of the clays

formation of secondary carbonates and native sulphur in sulphate rich messinian strata sicily abstract microbially formed authigenic carbonates accompanied by native sulphur are present in the calcare solfifero below a thick succession of gypsum deposited during the messinian salinity crisis in sicily we sampled these carbonates and associated sulphur in five former sulphur mines to subject them to a detailed petrographic and geochemical study in order to explore their different modes of formation native sulphur formed in conjunction with microbial sulphate reduction which is reflected in its depletion in 34s 34s values as low as 2 vs v cdt and an enrichment of 34s in the residual sulphate 34s values as high as 61 the oxidation of organic matter by sulphate reduction increased alkalinity inducing precipitation of secondary carbonate minerals a set of authigenic limestones lacking sulphate minerals but characterized by pseudomorphs after gypsum and high 18o values as high as 9 vs v pdb reflects syngenetic mineral formation within evaporitic settings low 13c values as low as 52 vs v pdb reveal that these carbonate phases were formed by microbial sulphate reduction coupled to the oxidation of biogenic methane another set of authigenic carbonates that replaced sulphate minerals is typified by low 18o values as low as 4 these carbonates formed epigenetically during later diagenesis following compaction dissolution of gypsum or anhydrite by meteoric waters delivered the sulphate for microbial sulphate reduction low carbon isotope values of these carbonates 29 to 5 indicate that carbonate was derived from the oxidation of crude oil and possibly minor methane partly involving different degrees of admixture of dissolved carbonate from other sources although the studied rocks with their vast amounts of secondary carbonate minerals and sulphur seem to indicate a similar genesis at first glance having formed by biogeochemical transformations of sulphate and hydrocarbons this study reveals that these processes can occur at different times in variable geological environments

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

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

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

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

u pb zircon geochronology and tempo of the end permian mass extinction the mass extinction at the end of the permian was the most profound in the history of life fundamental to understanding its cause is determining the tempo and duration of the extinction uranium lead zircon data from late permian and early triassic rocks from south china place the permian triassic boundary at 251 4 0 3 million years ago biostratigraphic controls from strata intercalated with ash beds below the boundary indicate that the changhsingian pulse of the end permian extinction corresponding to the disappearance of about 85 percent of marine species lasted less than 1 million years at meishan a negative excursion in 13 c at the boundary had a duration of 165 000 years or less suggesting a catastrophic addition of light carbon

benthic foraminifera based reconstruction of the first mediterranean atlantic exchange in the early pliocene gulf of cadiz abstract upper miocene to lower pliocene sediment cores from integrated ocean drilling program iodp hole u1387c iodp expedition 339 have been studied the main goal of this study is to reconstruct initial mediterranean atlantic water exchange after the opening of the gibraltar strait in the early pliocene benthic foraminiferal assemblages are the focus of the palaeoceanographic analyses of this work a distinct faunal turnover indicates a considerable change of the depositional environment at the miocene pliocene boundary foraminiferal composition suggests high rates of organic carbon flux and poorly oxygenated sea floor environment for the basal late messinian interval in contrast earliest pliocene assemblages point to periodic advection of warm better ventilated and likely mediterranean sourced waters to the studied site parallel periodic changes in siphonina tubulosa globocassidulina subglobosa and planulina ariminensis and previously established sedimentological and geochemical records zr al 18o suggest a rather sluggish mediterranean outflow between 5 3 and 5 2 ma benthic foraminifera along with sedimentological and geochemical data thus provide the earliest indications of mediterranean atlantic water exchange following the opening of the gibraltar strait sandy layers become frequent towards the top of the interval these sediments are rich in shelf foraminifera reflecting episodes of turbidite deposition possibly caused by tectonic adjustments related to the opening of the gibraltar strait the allochthonous assemblages frequently contain cibicides lobatulus and c refulgens species that have been considered indicators of mediterranean outflow water mow in previous studies our results warrant for caution when applying these species as mow proxy in the fossil record if there is evidence for downslope transport

constraining the cause of the end guadalupian extinction with coupled records of carbon and calcium isotopes abstract a negative c 13 excursion in carbonate sediments near the guadalupian lopingian middle late permian boundary has been interpreted to have resulted from a large carbon cycle disturbance during the end guadalupian extinction event ca 260 ma however the carbon isotope data alone are insufficient to uniquely determine the type and magnitude of perturbation to the global carbon cycle calcium isotopes can be used to further constrain the cause of a carbon isotope excursion because the carbon and calcium cycles are coupled via caco3 burial in this study we present coupled carbon and calcium isotope records from three guadalupian lopingian g l sections in china penglaitan and chaotian and turkey koserelik tepe the c 13 and ca 44 40 records differ among our studied sections and do not co vary in the same manner no section shows c 13 and ca 44 40 changes consistent with massive rapid volcanic co2 emissions or methane clathrate destabilization additionally many sections with large 3 changes in c 13 exhibit o 18 evidence for diagenetic alteration only one section exhibits a large excursion in the ca 44 40 of limestone but the absence of a similar excursion in the ca 44 40 of conodont apatite suggests that the limestone excursion reflects a mineralogical control rather than a perturbation to the global calcium cycle hence we interpret the large isotopic changes observed in some sections to have resulted from local burial conditions or diagenetic effects rather than from a large carbon and calcium cycle disturbance perturbations to the global carbon and calcium cycles across the g l transition were much less intense than the disturbances that occurred across the subsequent permian triassic boundary this finding is consistent with the much smaller magnitude of the end guadalupian extinction relative to the end permian

structural trends and palaeogeography of the central and western sicily belt new insights the geology of the sicilian mainland is summarized by n s geological sections a continuous late cenozoic orogenic belt through central and western sicily resulted from a complex deformative history recorded by several tectonic events the deformation mainly involved the sedimentary cover of the old african continental margin formed in a large basinal area bordered at its southern margin by a shallow water carbonate environment attached to gondwana the orogenic belt involves a complex architecture of thrust systems of different size geometry and palaeogeographical origin deformation which mainly developed in the earlier stages of thrusting in the basinal rock assemblages mainly gave rise to a stack of three different duplex structures respectively composed of palaeozoic mesozoic palaeogene and neogene strata large scale clockwise rotation of the thrusts predated transpressional movements in the hinterland during the latest miocene to pliocene high angle reverse faults with lateral components modified earlier tectonic contacts within the allochthons contemporaneous southwards directed imbrications affected the external southern areas progressively incorporating foreland and piggyback basirts the stratigraphic relationships of basin fills to the tectonic structures reveals that reactivation processes have been active during the last plio pleistocene

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

biomarker and isotope evidence for microbially mediated carbonate formation from gypsum and petroleum hydrocarbons along the western coast of the gulf of suez large amounts of evaporitic gypsum of miocene age have been microbially transformed into carbonates and elemental sulfur in the presence of petroleum similar diagenetic transformations have been described from numerous sites worldwide but the role of petroleum specifically as a carbon source for the sulfate reducing microbial community remains elusive we carried out a geochemical investigation of microbial carbonates from the gulf of suez that suggests the presence of a community of sulfate reducing bacteria thriving on carbon substrates contained in petroleum specifically a set of non isoprenoidal macrocyclic glycerol diethers mcgds that we tentatively ascribe to sulfate reducing bacteria have a stable carbon isotope composition close to that of petroleum n alkanes associated with the carbonates the presence of archaeol that is 13c enriched relative to bacterial lipids suggests that archaea are present but either indirectly involved or not involved in the transformation of petroleum derived carbon the lipid biomarker pattern we observe is distinct from those observed in settings where sulfate reduction is coupled to the anaerobic oxidation of methane our results suggest that petroleum migration has triggered the microbial transformation of gypsum into carbonates in the gulf of suez by extension the involvement of petroleum in the microbial transformation of gypsum into carbonates in other settings which was suggested by more indirect geological and inorganic geochemical evidence seems very likely

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

lithofacies and faunal succession faunal phase analysis as a tool in unravelling climatic and tectonic signals in marginal basins messinian miocene sicily many basins are filled under the influence of tectonics and variable climatically driven processes unravelling the relative contributions of these is generally easier in fossiliferous sequences if faunal diversity patterns are considered in conjunction with lithofacies analysis this approach has been successfully applied to late miocene strata of sicily where progressive restriction and desiccation within the sicilian caltanissetta region occurred under a semi arid climate during the messinian stage this restriction was partly due to antarctic cooling which produced palaeo mediterranean sea level oscillations during the early messinian as a prelude to closure of the atlantic connections in addition regions within this afro european plate collision zone were also subjected to syndepositional tectonic deformation associated with progressive perched basin development above foreland south verging thrust sheets the relative impacts of climatic eustatic versus tectonic control on sedimentation patterns within these perched basins has been debated at length however progress towards resolving this problem by a combined approach involving lithofacies analysis and faunal phase analysis provides clues for separating the effects of the controlling factors faunal phase analysis identifies general faunal associations with minimal emphasis on species diversity the resulting phase plots for early messinian strata appear to be transgression skewed when controlled by eustatic cyclicity and regression skewed when driven by regional tectonics associated with perched basin tectonics

the carbon isotope excursion on gssp candidate section of lopingian guadalupian boundary an isotopic stratigraphically well documented outcrop in penglaitan guangxi province south china has been proposed as a candidate gssp for the lopingian guadalupian boundary correlatable outcrops from the west wing tieqiao section and east wing penglaitan section of the laibin syncline exhibit synchronous excursions in carbon isotopes the isotopic excursions 13c show the best placement of the boundary may lie at the base of bed 6k which coincides with the clarkina postbitteri conodont zone and with eustatic change 13c increases during the uppermost guadalupian jinogondolella granti conodont zone from the top of 3c to the base of 6i a 13c peak value of 5 is located at the transition between these two conodont zones and is suggested as a proxy for the transition from transgression to regression a gradual depletion of carbon isotopes occurs in the c postbitteri zone from bed 6e to 7b and this gradual 13c excursion also suggests the sequences around the guadalupian lopingian boundary at the candidate section are conformable during the middle later c postbitteri zone a 3 5 dramatic 13c depletion is recorded at the tieqiao section but only a 2 depletion at the deeper facies penglaitan section synchronous with conodont zones that mark eustatic changes

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

permian palaeogeographic evolution of the jiangnan basin south china abstract the most striking geographic feature of the permian of south china is the jiangnan basin which intimately reflects the interplay between the yangtze and cathaysia blocks geographic and sedimentological evolution suggests that the jiangnan basin superposed on a precambrian collisonial megasuture and a folded early paleozoic deep basin was an extensional intracratonic basin it opened in the longlinian and became more passive and restricted in the latest maokouan the remarkably similar geographic patterns of the jiangnan basin in the early and late palaeozoic suggest that the yangtze and cathaysia blocks were coherent during the paleozoic

the western tyrrhenian sea revisited new evidence for a rifted basin during the messinian salinity crisis abstract in the last fifty years the messinian salinity crisis msc has been widely investigated in the mediterranean sea but a major basin remains fewly explored in terms of msc thematic the western tyrrhenian basin the rifting of this back arc basin is considered to occur between the middle miocene and the early pliocene thus including the msc giving a unique opportunity to study the crisis in a context of active geodynamics however the msc seismic markers in the western part of the tyrrhenian sea have only been investigated in the early eighties and the msc event in the western tyrrhenian basin remains poorly studied and unclear in this study we revisit the msc in the western tyrrhenian basin i e along the eastern sardinian margin we present results from the interpretation of a 2400 km long hr seismic reflection dataset acquired along the margin during the metyss research cruises in 2009 and 2011 the maps of the msc seismic markers reveal that the eastern sardinian margin was already dissected in structurals highs and lows during the msc we also demonstrate that the msc markers constitute powerfull time markers to refine the age of the rifting which ended earlier than expected in the east sardinian basin and the cornaglia terrace these results allow us to discuss the palaeo water depth of the western tyrrhenian basin during the msc as well as implications for possibles scenarios of the messinian salinity crisis across the eastern sardinian margin

mass extinctions and sea level changes abstract review of sea level changes during the big five mass extinctions and several lesser extinction events reveals that the majority coincide with large eustatic inflexions the degree of certainty with which these eustatic oscillations are known varies considerably thus the late ordovician and end cretaceous extinctions are associated with unequivocal major regressions demonstrated from numerous widespread regions in contrast the multiple high frequency sea level changes reported for the frasnian famennian crisis based on the supposed depth preferences of conodont taxa have little support from sequence stratigraphic analyses which reveals the interval to be one of highstand the end permian mass extinction has long been related to a severe first order lowstand of sea level newell n d 1967 revolutions in the history of life geol soc am spec pap 89 63 91 based primarily on the widespread absence of latest permian ammonoid markers but field evidence reveals that the interval coincides with a major transgression newell s hypothesis that marine extinctions are related to shelf habitat loss during severe regression remains tenable for the end guadalupian and end triassic extinction events but not for other crises rapid high amplitude regressive transgressive couplets are the most frequently observed eustatic changes at times of mass extinction with the majority of extinctions occurring during the transgressive pulse when anoxic bottom waters often became extensive the ultimate cause of the sea level changes is generally unclear a glacioeustatic driving mechanism can only be convincingly demonstrated for the end ordovician and end devonian events at other times it is speculated that they may relate to the widespread regional doming and subsequent collapse caused by the impingement of superplumes and ultimate eruption on the base of the lithosphere

chemostratigraphy and palaeo environmental characterisation of the cambrian stratigraphy in the amadeus basin australia abstract the sedimentary succession of the central australian amadeus basin consists of neoproterozoic to carboniferous sedimentary rocks and contains shallow marine subtidal carbonates of middle to late series 2 to furongian cambrian age a combination of sequence stratigraphy geochemistry and mineralogy shows a transgressive 2nd order cyclicity deposited between 511 490 ma and a change from arid low energy to humid high energy depositional environments this is reflected in an initially evaporitic sequence with upward decreasing halite and anhydrite abundance and transition from oxygenated to anoxic conditions reflected by the fe mineral species change from hematite to pyrite during transgression sequence boundaries of several 3rd order cycles consisting of hst carbonate rocks and lst siltstones correlate with globally recognised sequence boundaries linked to the inferred eustatic sea level record for the upper two series of the cambrian system the carbon isotope record for this 1400 m thick succession in combination with biostratigraphic age correlation allowed the identification of the globally recognised steptoean positive carbon isotope excursion spice drumian carbon isotope excursion dice and redlichiid olenellid extinction carbon isotope excursion roece

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

hypersaline conditions during deposition of the calcare di base revealed from archaeal di and tetraether inventories abstract the calcare di base is a widespread messinian carbonate formation in the mediterranean especially in sicily and calabria italy the environmental conditions under which these limestones were deposited their formation mechanism and the timing of deposition are a matter of debate in order to shed new light on their formation the lipid biomarker inventories of calcare di base from four locations in sicily and calabria were studied following petrographical and mineralogical characterization of the limestone samples the mineralogy is chiefly calcite the microfabric is mostly peloidal and partly laminated or brecciated deposition took place at high salinity as confirmed by numerous pseudomorphs after halite long chain n fatty acids were the most abundant lipid biomarkers in samples from all sites but isoprenoid alcohols were also abundant the most prominent archaeal compounds were diphytanyl glycerol diethers dgds and glycerol dibiphytanyl glycerol tetraethers gdgts among these archaeol and gdgt 0 caldarchaeol predominated respectively other gdgts were virtually absent minor amounts of c 20 25 dgd extended archaeol a biomarker for halophilic archaea were detected in all samples the 13 c values of caldarchaeol avg 20 and archaeol avg 11 varied widely indicating that these compounds derived from distinct archaeal precursor lipids based on lipid biomarker patterns the calcare di base had been previously considered to represent a normal marine deposit in contrast to the evaporitic gypsum and halite deposits in messinian successions the archaeal biomarker inventories from the calcare di base samples reported here in conjunction with the occurrence of pseudomorphs after halite reveal that deposition took place in a hypersaline environment

late miocene events in the mediterranean as recorded by carbonate evaporice relations the messinian stage in the mediterranean region is known mainly because of a major evaporitic event whose causes and global implications are still under discussion correlations between basinal evaporite bearing series and marginal carbonate platforms allow for improvement of the classical depostional models especially concerning the eustatic control of the environmental changes in the mediterranean these changes were controlled by the interplay of aperiodic and periodic factors 1 tectonics related to the relative motions of the african and eurasian plates and resultant linear increase in the basin restriction 2 sea level fluctuations that alternately aggravated the restriction or allowed marine replenishment and 3 climatic fluctuations that controlled the level of the mediterranean during stages of isolation the messinian sedimentary succession reflects a typical sequence of progressive isolation marine marls yields laminites yields transitional deposits yields evaporites yields lacustrine deposits the first stage of the so called salinity crisis was characterized by a mediterranean lowstand that resulted in erosion of former platforms and deposition of the lower evaporites during the next stage sea level rose tb3 3 cycle high enough to temporarily replenish the basin cyclic upper evaporites with development of stromatolite rich deposits finally the uppermost messinian freshwater to brackish lacustrine deposits reflect both themore cessation of sea water input maximum tectonic isolation low sea level and freshwater input related to increasing runoff less

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

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

the record of the messinian salinity crisis in mobile belts insights from the molise allochthonous units southern apennines italy abstract mediterranean marginal basins recorded the messinian salinity crisis msc in various structural settings including syn rift thrust top foredeep and foreland basins during the msc the apennines were one of the mobile belts of the peri mediterranean chain starting from more hinterland areas allochthonous units of both the northern and southern apennines migrated toward the adriatic foreland developing allochthonous top sedimentary basins one of these basins on top of the molise allochthonous units southern apennines recorded almost all of the main steps of the msc in a gypsum quarry district the occurrence of conduits yielding flow mobilized sediments which cross cut the lower evaporites testifies to a fluid migration event responsible for the formation of a brecciated mudgrade limestone buildup this event can be connected with the mediterranean drawdown responsible for the messinian erosional surface mes the post evaporitic marly succession that unconformably overlies the lower evaporites and the brecciated limestones is characterized by the presence of paratethyan molluscs and ostracods loxoconcha muelleri and loxocorniculina djafarovi zones and small mammals among which is recorded the occurrence of stephanomys debruijni a disconformity within the post evaporitic succession divides it into lower p ev1 and upper p ev2 lago mare deposits a further erosional surface separates the messinian lago mare sediments from fully marine lower zanclean mpl2 zone deposits whilst the unconformity separating the lower evaporites and the lago mare deposits although enhanced by a tectonic event could be related to a late messinian base level drop mes1 as well as the disconformity between p ev1 and p ev2 mes2 the younger angular unconformities affecting both the lago mare deposits p ev2 and the fully marine pliocene sediments might be related to two different phases of orogenic transport those events affected the molise allochthonous units during their late miocene early pliocene forelandward migration

the messinian succession of the crotone basin southern italy ii facies architecture and stratal surfaces across the miocene pliocene boundary the upper messinian to lower zanclean succession of the crotone basin a forearc basin located along the ionian side of the calabrian arc southern italy consists of a turbidite bearing succession the petilia policastro formation overlying evaporites and abruptly passing upward into coarse grained continental deposits the carvane conglomerate which are in turn overlain by distal shelf to slope mudstones the cavalieri marl the marked environmental changes from subaqueous to continental and vice versa documented by the studied succession are inferred to be the expression of basin scale tectonics leading to uplift and exposure superposed on the mediterranean scale base level rise that followed the acme of the messinian salinity crisis the upper part of the succession documents a transgressive trend probably initiated within the carvane conglomerate and further testified by the presence of a ravinement surface marked by a transgressive lag at the base of the zanclean cavalieri marl pointing to a non catastrophic deepening occurred near the end of the messinian

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

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

gas hydrate dissociation in the lorca basin se spain during the mediterranean messinian salinity crisis abstract the tortonian marls which were deposited in the lorca basin se spain prior to the messinian tripoli formation contain discontinuous levels of indurated nodules and massive layers up to a few meters thick of diagenetic dolomite the oxygen and carbon isotopic compositions of these dolomites indicate that the carbonate diagenesis occurred mostly in 13c rich and 18o rich to 18o poor solutions the vertical distribution of the values of these dolomites is interpreted as the result of the past occurrence of gas hydrate reservoirs where the methane source probably originated from the organic rich marls we postulate that the gas hydrates contained in the tortonian marls were destabilized during the water level drops related to the messinian salinity crisis associated sedimentary structures include numerous syn sedimentary deformations and brecciation which are the expression of important sedimentary instabilities which could have been generated during the gas hydrates decomposition

the guadalupian lopingian boundary permian in a pelagic sequence from panthalassa recognized by integrated conodont and radiolarian biostratigraphy abstract guadalupian lopingian sedimentary rocks are widely distributed in accretionary complexes in japan but the guadalupian lopingian boundary g lb is not well documented from these pelagic sediments to identify the g lb and to better correlate an extinction event that occurred around the guadalupian lopingian boundary we examined the conodont biostratigraphy from a permian pelagic chert sequence in the gujo hachiman section gifu southwest japan age diagnostic conodonts including clarkina postbitteri postbitteri were found in this section the biostratigraphic occurrences of these age diagnostic conodonts can pinpoint the g l transitional zone in the gujo hachiman section by comparison with well studied sections from south china including the gssp section the transitional zone was recognized by the first occurrence horizons of both clarkina postbitteri hongshuiensis and c p postbitteri the g lb has been placed at or above the first occurrence horizon of the radiolarians albaillella yamakitai or albaillella cavitata in previous studies from china and japan we detected the first occurrence horizon of a yamakitai below the base of the g l transitional zone in the upper capitanian the conodont biostratigraphy is consistent with the radiolarian biostratigraphy in this section which can be correlated to relevant sections in china

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

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

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

the mid capitanian middle permian mass extinction and carbon isotope record of south china abstract conodont c isotope and fossil and facies data are presented for the capitanian middle permian mass extinction record seen in platform carbonates maokou and wuchiaping formations of south china where limestones interdigitate with the volcanic succession of the emeishan large igneous province the maokou formation provides an extinction record marked by the loss of keriothecal walled fusulinaceans and a turnover in calcareous algae in sections within the emeishan province this crisis occurs at the base of the oldest record of volcanism from the jinogondolella altudaensis conodont zone of mid capitanian age around the periphery of the emeishan province this extinction level lies within the upper part of the maokou formation at a level where platform carbonate deposition was frequently interrupted by thick volcanic ash depositional events the assemblages of the uppermost maokou formation are characterised by typical late permian taxa although these levels still lie within the middle permian guadalupian series disaster taxa such as earlandia and diplosphaerina are locally prolifically abundant in the aftermath of the mass extinction the crisis is particularly noteworthy amongst photosynthetic taxa such as calcareous algae and fusulinaceans that probably harboured photosymbionts therefore a kill mechanism involving cooling from explosive volcanism and potentially acid rain from sulphate aerosols appears appropriate a composite 13ccarb curve calibrated against a high resolution conodont biostratigraphy reveals a major intra capitanian negative excursion of 5 superimposed on typically heavy 4 5 middle permian values this curve can also be recognised in panthalassan seamount carbonates of japan although this requires reassignment of apparently upper permian limestones to the middle permian in both china and japan the capitanian mass extinction occurs during the early stage of this major intra capitanian negative excursion assuming typical platform carbonate accumulation rates the records of the maokou formation suggest 13ccarb values fell at 0 01 kyr suggesting a catastrophic origin such as gas hydrate destabilisation is unlikely although a volcanic source is possible

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

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

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

an archaeal biomarker record of paleoenvironmental change across the onset of the messinian salinity crisis in the absence of evaporites piedmont basin italy abstract a sudden change from normal marine to extreme paleoenvironmental conditions occurred approximately 6 ma ago in the mediterranean basin at the onset of the late miocene messinian salinity crisis one of the most severe ecological crises in earth history strong evaporation and tectonics led to hypersaline conditions resulting in widespread deposition of evaporites and the apparent annihilation of the marine metazoan biosphere in contrast to the prominent occurrence of evaporites elsewhere in the mediterranean evaporites did not form in the deeper part of some marginal basins at the onset of the crisis the strata of the pollenzo section piedmont basin nw italy studied here were deposited in such a paleogeographic setting instead of evaporites a cyclic succession of organic rich shales and carbonates formed during the early phase of the crisis in the study area these sediments record a sharp increase in the contents of archaeal molecular fossils that are mostly represented by isoprenoidal dialkyl glycerol diethers dgds and isoprenoidal glycerol dialkyl glycerol tetraethers gdgts such an expansion of archaeal biomass is best explained by a change of the archaeal communities at the onset of the messinian salinity crisis in particular the appearance of molecular fossils of extremophilic archaea mostly producing dgds archaeol and extended archaeol suggests the emergence of halophilic archaea at the same time lipids of planktonic thaumarchaeota especially crenarchaeol are present across the entire section suggesting the local persistence of normal marine conditions in agreement with the sudden appearance of tetrahymanol in the upper part of the section the persistence of crenarchaeol indicates the establishment of water column stratification after the advent of the messinian salinity crisis to further investigate the piedmont basin paleoenvironmental conditions we test the archaeol caldarchaeol ecometric ace a proxy developed for identifying high paleosalinities in waters and possibly in sediments despite high ace values found for the messinian salinity crisis samples these values are in contrast with the absence of any lithological evidence for high salinities as well with other biomarker independent information indicating low to normal seawater salinities this apparent contradiction is likely explained by the complexity of the sources of archaeal lipids especially of caldarchaeol and archaeol limiting the utility of the ace for the reconstruction of paleosalinities for messinian strata

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

isotopic compositions of diagenetic dolomites in the tortonian marls of the western mediterranean margins evidence of past gas hydrate formation and dissociation abstract previous studies in the lorca basin s e spain sediment geol 2002 have shown that the diagenetic dolomitic concretions from the tortonian marls are related to the past occurrence of gas hydrates which were rapidly dissociated when the sea level dropped during the messinian salinity crisis these conclusions were based on the oxygen and carbon isotopic compositions of these dolomites which indicated that the carbonate diagenesis occurred either in 13 c rich 18 o poor solutions as it is typical in gas hydrate systems or in 13 c poor 18 o rich solutions generated during gas hydrate decomposition we have recently discovered similar dolomitic nodules in other tortonian marly successions from s e spain and northern morocco the oxygen and carbon isotopic compositions of the diagenetic dolomites from these areas in spain and morocco are very similar to those from the lorca basin this demonstrates that the dolomitic nodules from the tortonian marls of the betic and rifian basins were all related to the same diagenetic environments where pore fluids were modified by gas hydrate formation dissociation processes these overall observations in s e spain and northern morocco suggest that the dissociation of gas hydrates during the messinian salinity crisis was not a local phenomenon but corresponded to a major event which affected both sides of the western mediterranean margins it might have been initiated during the first major restriction step that started around 6 7 ma in the mediterranean sea and probably climaxed at 5 9 ma when the mediterranean sea level dropped by more than 1000 m during the salt deposition stage

geochemical indicators in western mediterranean messinian evaporites implications for the salinity crisis abstract the messinian salinity crisis msc led to deposition of one of the youngest saline giant on earth the increasing restriction of the connections between the mediterranean the atlantic ocean and the freshwater paratethyan basins resulted in the deposition of massive amounts of evaporites gypsum anhydrite halite and potash salts in shallow marginal basins as well as in deep mediterranean basins here we show that each gypsum unit in the circum mediterranean marginal basins in sicily and spain is characterized by a narrow range of sulfate isotopic values 34s 23 and 18o 14 in the lower gypsum 34s 23 and 18o 17 in the upper gypsum sulfate isotope compositions found in msc evaporites from a variety of circum mediterranean basins are homogenously high relative to expected late miocene marine evaporites 34s 22 and 18o 12 this points to a stratified mediterranean sea with a high salinity dense and anoxic bottom water mass an intermediate depth gypsum saturated brine flooded marginal basins from which selenite deposits formed during the msc stage 1 primary lower gypsum and msc stage 3 upper gypsum messinian brines were gradually affected by biogenic redox processes and isotopically differentiated from global seawater values the homogeneity of isotopic signatures between distant synchronous gypsum deposits further supports the deep basin deep water model for the mediterranean during the entire msc event

pattern of marine mass extinction near the permian triassic boundary in south china the meishan section across the permian triassic boundary in south china is the most thoroughly investigated in the world a statistical analysis of the occurrences of 162 genera and 333 species confirms a sudden extinction event at 251 4 million years ago coincident with a dramatic depletion of 13ccarbonate and an increase in microspherules

carbonate replacements after sulfate evaporites in the middle miocene of egypt abstract massive zones of diagenetic carbonate which replace sulfate deposits are observed in the middle miocene evaporites in several outcrops along the egyptian coast of the gulf of suez these carbonates display marked similarities of morphology lithofacies and stable isotope composition to diagenetic carbonates described in some portions of messinian gessoso solfifera formation of sicily and in the castiles of the upper permian castile formation of the delaware basin the mechanism of mineral transformation is basically bacterial sulfate reduction because the low 13c values of these carbonates argue for the organic origin of carbon the 18o values fall i to two distinct groupings indicating that the carbonates were crystallized during two different diagenetic stages the early diagenetic stage occurred soon after deposition in pore waters of marine origin and at different levels of evaporation organic matter used by bacteria was produced in situ the late diagenetic stage occurred when the tectonic or halokinetic uplift of the sequence caused flushing of the sediments by groundwaters of the phreatic aquifer and hydrocarbon migration furthermore to explain the very low 18o values of these carbonates it is inferred that locally ambient temperatures reached more than 35 c due to the large quantities of energy released during the bacterial sulfate reduction

soil development on sediments and evaporites of the messinian crisis abstract vast areas in the mediterranean are characterised by evaporite deposits of the messinian crises c 6 5 3 ma bp during this period large deposits were built up in shallow lagoon like systems and are now found in southern italy albania cyprus and turkey so far soil formation on evaporites has been studied predominantly in subarid to arid environments although the formation of soils has received new significance little is known about the evolutional trajectories on evaporites of the mediterranean we therefore studied soil formation in the caltanissetta basin sicily where evaporites are most widespread the lithologies included the sequence marine clay deposits laminated marl diatomite tripoli sediments calcare di base limestone detritic deposits gypsum selenite the chemical signature immobile elements rare earth elements indicated that they all have a similar origin surprisingly both an increasing corg and carbonate content in the soils caused a decrease in the 13c signal in carbonates and in part in the bulk soil the low 13c and 18o values of carbonates in the parent material indicate a high rock water or meteoric water interaction that has occurred during sedimentation and diagenesis organic matter was oxidised into the shallow lagoon like systems and its carbon incorporated in the limestone elemental leaching from silicates during pedogenesis was most intense in the soils that developed on clays and tripoli sediments vertisols and mollisols have evolved together with a high amount of oxyhydroxides non crystalline and crystalline forms and kaolinite only weak soil formation was recognisable at sites having gypsiferous parent material the presence of a high amount of selenite hindered a more advanced evolution the soils developed on detritic and gypsiferous material exhibited some palygorskite that was inherited from the parent material at sites having selenite or limestone shallow aridisols or mollisols are found weathering is weakly pronounced e g indicated by a high proportion of trioctahedral minerals besides inheritance from the parent material smectite and kaolinite are also actively formed in the soils with increasing weathering plagioclase and mica are the main sources of smectite and k feldspar is a main source of kaolinite neo formation the evaporite deposits vary greatly within short distances causing a high spatial diversity of soils consequently soil quality strongly varies which challenges agricultural use well developed soil profiles and advanced weathering stages are only possible when marine clays tripoli sediments or detritic deposits are the parent material limestone calcare di base and gypsiferous sediments selenite strongly limit soil formation and mineral transformation

age refinement of the messinian salinity crisis onset in the mediterranean we propose a revised age calibration of the messinian salinity crisis onset in the mediterranean at 5 971 ma based on the recognition of an extra gypsum cycle in the transitional interval of the perales section sorbas basin spain and the revision of the magnetostratigraphy of the monticino section vena del gesso basin italy this age re calibration allows to state more accurately that i the interval encompassing the msc onset is continuous thus ruling out any erosional feature or stratigraphic hiatus related to a major sea level fall affecting the mediterranean ii the first gypsum was deposited during the summer insolation peak at 5 969 ma associated with an eccentricity minimum and roughly coincident with glacial stage tg32 iii the msc onset was preconditioned by the tectonically driven reduction of the hydrological exchanges with the atlantic ocean and finally triggered by glacial conditions in the northern hemisphere and by arid conditions in northern africa

sicily s fold thrust belt and slab roll back the si ri pro seismic crustal transect sicily is a thick orogenic wedge formed by 1 the foreland african and its sicilian orogen and 2 the thick skinned calabrian peloritani wedge the crust under central sicily from the tyrrhenian margin to the coastline of the sicily channel has been investigated by the multidisciplinary si ri pro research project the project dealt with the nature and thickness of the crust and depth and geometry of the moho which is essential in formulating subduction models and improving the knowledge of african and tyrrhenian european lithospheres the results resolve features such as 1 the main orogenic wedge 2 the very steep nw se trending regional monocline suggesting inflection of the foreland crust 3 the deep caltanissetta synform imaged for the first time to about 25 km and 4 the top of the crystalline basement and the inferred crust mantle boundary the si ri pro transect confirmed that the nnw dipping autochthonous iblean platform of se sicily and its basement extends all the way into central sicily further nw towards the nnw end of the transect a large uplift involves the iblean platform and its underlying basement the associated gravity anomaly is interpreted as the southern wedge edge of the tyrrhenian mantle that splits the subducting iblean pelagian african continental slab from an overlying synformal stack of allochthonous thrust sheets supplementary materials additional data are available at www geolsoc org uk sup18594

fast deep sinking in mediterranean eddies i large up to 0 03 m s 1 downward vertical water velocities w are observed using yearlong moored adcp at 2400 m in the deep mediterranean sea s algerian basin once every 2 3 months w rapidly increases to o 0 01 0 002 m s 1 before slowly decreasing during a few weeks in association with the passage of mesoscale eddies formed nearby these amplitudes of negative w are o 100 times larger than those commonly linked to mesoscale eddies near the surface subduction and o 10 times larger than settling velocities for marine snow our observations suggest that mesoscale eddies which are important for biological productivity near the surface can also convect nearly fresh material down to the bottom 3000 m there within a few days

origin and diagenetic evolution of gypsum and microbialitic carbonates in the late sag of the namibe basin sw angola abstract ephemeral evaporitic conditions developed within the uppermost part of the transgressive late sag sequence in the namibe basin sw angola leading to the formation of extensive centimetre to metre thick sulphate bearing deposits and correlative microbialitic carbonates rich in pseudomorphs after evaporite crystals the onshore pre salt beds examined in this study are located up to 25 m underneath the major mid aptian evaporitic succession which is typified at the outcrop by gypsiferous bambata formation and in the subsurface by the halite dominated loeme formation carbonate evaporite cycles mostly occur at the top of metre thick regressive parasequences which progressively onlap and overstep landward the former faulted rift topography or fill major pre salt palaeo valleys the sulphate beds are made up of alabastrine gypsum associated with embedded botryoidal nodules dissolution related gypsum breccia and are cross cut by thin satin spar gypsum veins nodular and fine grained fabrics are interpreted as being diagenetic gypsum deposits resulting from the dissolution and recrystallisation of former depositional subaqueous sulphates whereas gypsum veins and breccia result from telogenetic processes the carbonates display a broader diversity of facies characterised by rapid lateral variations along strike thin dolomitic and calcitic bacterial mediated filamentous microbialitic boundstones enclose a broad variety of evaporite pseudomorphs and can pass laterally over a few metres into sulphate beds dissolution related depositional breccias are also common and indicate early dissolution of former evaporite layers embedded within the microbialites sulphate and carbonate units are interpreted as being concomitantly deposited along a tide dominated coastal supra to intertidal sabkha and constitute high frequency hypersaline precursor events prior to the accumulation of the giant saline mid aptian bambata and loeme formations petrographic and geochemical analyses reveal successive dissolution recrystallisation and cementation phases that occurred during burial uplift and exhumation implying a complex diagenetic evolution of both gypsum and carbonates influenced by pore fluids of diverse composition which distinctly varied from meso to telogenetic domains

volcanism mass extinction and carbon isotope fluctuations in the middle permian of china the 260 million year old emeishan volcanic province of southwest china overlies and is interbedded with middle permian carbonates that contain a record of the guadalupian mass extinction sections in the region thus provide an opportunity to directly monitor the relative timing of extinction and volcanism within the same locations these show that the onset of volcanism was marked by both large phreatomagmatic eruptions and extinctions amongst fusulinacean foraminifers and calcareous algae the temporal coincidence of these two phenomena supports the idea of a cause and effect relationship the crisis predates the onset of a major negative carbon isotope excursion that points to subsequent severe disturbance of the ocean atmosphere carbon cycle

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

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

variability of the δ13c of dissolved inorganic carbon at a site in the north pacific ocean abstract we present a depth profile of 13 c dic dissolved inorganic carbon and a time series of surface water 13 c dic from seawater samples collected at a single site during the eve cruise in the north pacific in june of 1987 our deep water results confirm those reported by kroopnick 1985 for geosecs station 213 10 west of eve site we observed a small but significant decrease in the 13 c of dic in the upper 500 m of the water column over 13 years since the geosecs survey this is likely due at least in part to the input of additional fossil fuel derived co 2 to the upper ocean we observed a significant change in surface water 13 c over a short time period 2 days that was the result of a change in the shallow surface water mass this change emphasizes the need for caution when conducting seasonal studies

progress problems and prospects an overview of the guadalupian series of south china and north america abstract the guadalupian epoch is marked by the formation of the pangean supercontinent global sea level change rifting and drifting of the cimmerian continents formation of large igneous provinces and dramatic biotic changes a high resolution biostratigraphic chemostratigraphic and high precision geochronologic framework of this critical transition is fundamental to understanding these events extensive studies of the latest cisuralian and guadalupian series in both south china and north america reveal the same conodont lineages but the conodont interval zones based on jinogondolella within the guadalupian series are slightly diachronous high precision u pb geochronological studies ca id tims method calibrate the base of the guadalupian series base roadian at 273 01 0 14 ma a previously reported age from an ash bed overlying the emeishan flood basalts 259 51 0 21 ma is adopted for the guadalupian lopingian boundary glb based on recently published geochronology and bayesian age modeling from the guadalupian series the base of the capitanian is constrained at 264 28 0 16 ma and the base of the wordian is interpolated to be 266 9 0 4 ma the illawarra reversal is of early middle wordian age both north america and south china possess a distinct negative 13ccarb excursion of 3 5 at the latest kungurian and early roadian lk er cie which coincides with the early stages of a significant 3rd order sea level rise the large end guadalupian 13ccarb negative excursion may have been affected by post depositional diagenesis or a warming event associated with the emeishan volcanism the 87sr 86sr ratios in both regions declined from the latest kungurian to the late capitanian but have different ratios and reveal several fluctuations in the middle guadalupian measured 18oapatite values suggest that the delaware basin was 3 4 c cooler than the eastern yangtze block analysis of a new high resolution database of marine taxa indicates only a minor pre lopingian diversity drop from 261 04 ma to 259 98 ma which coincides with the peak emeishan volcanism the widely perceived end guadalupian mass extinction in north america is evidently masked by and possibly an artefact of a stratigraphic truncation effect due to rapid lithofacies changes from limestone to laminated evaporites with the closure of the west texas basins

interpreting carbon isotope excursions carbonates and organic matter abstract variations in the carbon isotopic compositions of marine carbonate and organic carbon provide a record of changes in the fraction of organic carbon buried through time and may provide clues to changes in rates of weathering and sources of organic carbon paired carbonate and organic carbon isotope determinations provide a possibility of interpreting not only changes in the global carbon cycle through time but changes in atmospheric pco2 as well interpretations of these types of data are typically rather qualitative a quantitative basis is required to develop a better understanding of changes in the carbon cycle for this purpose we employ a simple model of the global carbon cycle which is subjected to a number of different perturbations each lasting 500 ky i e much longer than the residence times of carbon and phosphorus in the ocean atmosphere system in addition to standard considerations of carbon mass and isotopic fluxes to the ocean atmosphere system from weathering and volcanism and fluxes of organic carbon and carbonate carbon to sediments the model incorporates sensitivity of the photosynthetic carbon isotope effect to changes in pco2 the inclusion of this parameter leads to unexpected carbon isotope responses to forcing that causes increased rates of organic carbon burial a series of simple to more complex simulations illustrates the significant effects of varying differences between the carbon isotopic composition of sedimented carbonate and organic carbon b with constant b a 50 increase in organic carbon burial produces a parallel increase in carbonate and organic carbon isotopic compositions however the same simulation with b responsive to pco2 changes produces an initial parallel 13 c increase but this is followed by an even greater 13 c enrichment in organic carbon because pco2 falls in response to increased organic carbon burial the counterintuitive overall result of the enhanced organic carbon burial event is that the carbonate carbon isotopic composition actually decreases because of the more substantial increase in 13 c org in addition we illustrate the effects on carbon isotopic compositions of the oceanic inorganic carbon reservoir and buried organic matter of a 50 increase in volcanic co2 outgassing a 50 increase in weathering rate with coupled phosphate and riverine carbon flux responses a 50 decrease in shale associated organic carbon weathering a 50 decrease in silicate weathering rate and the possible effects of the rise in abundance of c4 plants in the late miocene to recent we compare the model simulated carbon isotopic responses for some of these experiments to paired carbonate and organic carbon records to illustrate how these records might be interpreted in light of the model response

geochemical events documented in inorganic carbon isotopes abstract screening of sampling and analytical data is crucial for the detection of real global shifts in marine 13c against the noise of diagenesis the real global shifts of 13c are of two types 1 long term secular shifts caused by changes in the fractional burial of organic carbon and 2 transient shifts caused by abrupt changes of biological productivity in the surface photic zone both are applicable to stratigraphic correlation but differ in their application to modelling of changes in oceanographic or atmospheric composition a recent compilation found 34 carbon isotope events in the phanerozoic and neoproterozoic equally distributed among positive and negative shifts this in itself attests to a variety of proximate causes of the shifts

biogenic carbonates are they a criterion for underlying hydrocarbon accumulations an example from the gulf of suez region egypt the gulf of suez petroliferous basin is characterized by the occurrence of a middle upper miocene evaporite cap field and subsurface investigations in the southwest gulf of suez region indicate that the evaporites usually contain two types of biogenic carbonates in addition to sulfur the first type of carbonate is biogenic syngenetic in origin and was formed in low temperature euxinic aquatic environments by the reduction of dissolved sulfates and the oxidation of organic matter by sulfate reducing bacteria the resulting carbonate and sulfur are stratigraphically restricted within the evaporite sequence and occur as interlaminated gypsum calcite sulfur or as sulfur ooids sulfur globules and stromatolitic sulfur that are enclosed in gypsum or calcite the biogenic syngenetic carbonate and sulfur did not originate from petroleum and have a significance of euxinic aquatic settings the second type of carbonate is a biogenic epigenetic carbonate that formed under low temperatures by biochemical reactions between seeping hydrocarbons and the overlying miocene evaporites the carbonate is vuggy is included within or caps the evaporites and usually shows hydrocarbon stains or emits a hydrocarbon smell the sulfur is usually yellow but may be brown to black due to bitumen staining carbonates replace gypsum or anhydrite and occur as aragonite calcite or dolomite the d13c mean values for carbonate minerals range from 7 8 to 27 2 pdb being relatively heavier than the d13c values of the nearby crude oil 28 1 to 29 3 pdb carbon isotope values indicate that these carbonates were formed from the heavier organic carbon dioxide under reducing conditions where the lighter methane is stable the occurrence of biogenic epigenetic carbonates and sulfur in the evaporite deposits of the gulf of suez petroliferous basin is similar to that recorded in other basins such as the gulf coast basins of texas louisiana and southern mexico the fergana and amudarya depression of central asia and the mesopotamian depression in iraq the biogenic epigenetic carbonates or sulfur in some regions is considered as a criterion for petroleum microseepage that may indicate a potential hydrocarbon bearing reservoir at depth