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

distinguishing climatic and tectonic signals in the sedimentary successions of marginal basins using sr isotopes an example from the messinian salinity crisis eastern mediterranean the evolution of oceanic 87 sr 86 sr through the tertiary has been sufficiently well documented to provide a useful stratigraphic tool for carbonate rich marine sediments which were deposited in basins connected to the global oceans in isolated basins sea water 87 sr 86 sr will diverge from coeval oceanic values thus if independent age information exists the geochemical signature can constrain the timing of isolation in marginal basins formed in tectonically active settings the timing of isolation is critical to the assessment of the relative importance of climate or tectonic controls on that event previously isolation has been assumed to coincide with the last occurrence of open marine fauna however in an example from the eastern mediterranean 87 sr 86 sr data challenge that assumption and can be interpreted as indicating a protracted period of isolation c 3 ma during which time marine conditions prevailed prior to the messinian salinity crisis at the end of the miocene this allows tectonic and climatic signals to be distinguished since although convergence of africa with eurasia was responsible for isolation of this part of the mediterranean it is more likely that later climatic change triggered desiccation

modelling the effect of evaporation on the salinity 87 sr 86 sr relationship in modern and ancient marginal marine systems the mediterranean messinian salinity crisis abstract palaeosalinity reconstructions in marginal marine environments based on sr isotope data assume simple two end member mixing of river and ocean water an improved model that incorporates the effect of evaporation is used to demonstrate that this approach is not valid in evaporation dominated systems however sr isotope records combined with faunal and lithological constraints on salinity can be used to assess the palaeohydrological conditions of ancient marginal marine systems this new method is used to interpret deviations from the global seawater sr isotope curve observed in mediterranean successions during and up to 3 myr prior to messinian evaporite deposition results suggest that no absolute change in the net evaporation flux is required to explain the three to four fold rise in salinity of mediterranean water at the carbonate evaporite transition modelled sr isotope records indicate that this increase in salinity was synchronous with an increase in the dominance of atlantic water inflow in the hydrological budget of the mediterranean the messinian salinity crisis may therefore have been the response to a marine transgression

late pleistocene fauna from zesch cave mason county texas the zesch cave local fauna is one of the most diverse fossil vertebrate localities from central texas and one of the only three sites on the edwards plateau juxtaposed to the llano uplift at least 70 vertebrate taxa are identified in this local fauna including fish four lissamphibians six sauropsids eight birds and fifty one mammal species a largely granitic structural dome the llano uplift differs from the rest of the predominantly carbonate edwards plateau in geology soils and ecology this is reflected in the zesch cave local fauna as well which has greater similarity to high plains faunas than those recorded 80 km or more to the south notably this local fauna contains the first record of sorex hoyi pygmy shrew and pica pica magpie from central texas which indicates similarity or connection with a rocky mountain fauna the zesch cave vertebrates provide a more complete picture of faunal zones as they existed in the rancholabrean

sr s and oso4 isotopes and the depositional environments of the upper miocene evaporites spain abstract upper miocene evaporites in the nijar basin southeastern spain contain thick massive and coarse crystalline selenites of the middle messinian yesares formation on the basis of their sedimentary fabrics and structures such as euhedral terminations of crystals well preserved algal filament inclusions and standing growth orientations these selenites are interpreted to be primary bottom growth deposits most of these selenites have sr concentrations of about 1000 ppm range from 700 to 1800 ppm 87sr 86sr values of yesares selenites vary between 0 70890 and 0 70896 n 18 which are all within the known range of messinian seawater suggesting a marine origin however quantitative modeling of 87sr 86sr vs sr ca of fluids demonstrates that a minor amount of admixed nonmarine fluid e g 20 might have contributed to the yesares marine brines 34s and 18oso4 values of yesares selenites range from 21 to 24 cdt and from 10 to 16 smow respectively these ranges are more variable and most values are heavier than those expected for normal miocene marine gypsum on the basis of quantitative modeling these heavy 34s and 18oso4 values have most likely resulted from reduction and oxidation reactions of sulfur species that occurred in brines rather than from contributions of nonmarine water or from reservoir crystallization effects the use of sr s and o isotopes provides a possible means of distinguishing whether an ancient evaporite was deposited by marine nonmarine or hybrid brines sr isotopes however are insensitive to minor nonmarine contributions on the basis of quantitative modeling and consequently marine sr isotopes for evaporites e g gypsum do not necessarily indicate pure marine depositional environments compared to sr isotopes 34s and 18oso4 of marine gypsum are even more insensitive to minor nonmarine contributions because of much higher so4 concentrations in seawater and seawater evaporated brines than in most freshwaters therefore sr o and s isotopes should be used with caution to interpret depositional environments and to determine parent fluids of ancient evaporites

the messinian marine to nonmarine gypsums of jumilla northern betic cordillera se spain isotopic and sr concentration constraints on the origin of parent brines the origin of the messinian hoya de la sima hs gypsum betic foreland is constrained using 87sr 86sr 34s sr concentration and petrographic data the lower and middle hs units consist of subaqueous vertically aligned and stromatolitic selenites the latter containing unusual microbial depositional textures the upper unit consists of very shallow water bioturbated lenticular gypsum with paracamelus ichnites 87sr 86sr and 34s indicate precipitation from predominantly marine waters with upward increasing continental influence mixing models between messinian seawater and continental water that dissolved triassic evaporites show that the percentages of seawater required to explain the measured 87sr 86sr are analogous to the percentages obtained using 34s supporting precipitation from such mixtures 87sr 86sr and 34s of lower hs selenites resemble those of the primary lower gypsum plg of the messinian salinity crisis msc in both cases indicating precipitation from seawater continental water mixtures in which most sr and so4 were supplied by messinian seawater in the lower hs selenites sr concentrations indicate contributing continental waters with sr ca ratios similar to seawater however sr concentrations of plg selenites from other betic basins bajo segura sorbas indicate parent waters with sr ca ratios lower than seawater if the sr contents of the betic plg selenites are representative it is unlikely that the lower hs selenites represent the plg however we cannot completely discard that option since different lpg subbasins could have had variable sr ca the hs gypsums formed coevally to diapirism of triassic evaporites in a restricted lagoonal basin developed during or slightly after a phase of strike slip faulting in the betic cordillera more general implications of this work are that sr concentrations combined with 87sr 86sr and 34s data provide key constraints on the origin of parent brines and using sr concentrations as paleosalinity proxy in gypsum precipitated from seawater continental water mixtures is inconclusive because they largely depend on the initial sr ca ratio of the brine this study also illustrates that the electron microprobe is ideal to obtain reliable spatially resolved sr concentration data in selenitic gypsum these data in combination with fluorescence petrography provide valuable criteria to discriminate primary depositional from diagenetic gypsum a critical step in the interpretation of geochemical data

sedimentary and tectonic evolution of the vena del gesso basin northern apennines italy implications for the onset of the messinian salinity crisis the integration of field and subsurface data permits a substantial revision of the sedimentary evolution of the vena del gesso basin a thrust top basin in the northern apennines where shallow water primary gypsum deposits related to the messinian salinity crisis were well developed and preserved as inferred from lateral and vertical facies changes within the underlying deep marine turbidites of the marnoso arenacea formation evaporite precipitation occurred in a basin bounded to the north and to the east by a thrust related anticline actively growing since the late tortonian both gypsum deposition and subsequent deformation were strongly controlled by evolving paleobathymetry driven by tectonics primary gypsum precipitated in a shallow silled basin while in the adjacent deeper and larger foredeep basin organic rich shales were deposited gypsum deposits underwent severe postdepositional deformation related to large scale gravitational collapse as a result of a regional uplift event also coincident with the end of the evaporitic phase along the inner shallower dipping limb of the anticline bounding the basin large scale poorly deformed gypsum slabs moved downslope along a detachment surface developed at the contact with the underlying euxinic shales forming both extensional and compressional features and showing an overall southwestern vergence the identification of a south southwest dipping paleoslope here pointed out for the first time suggests that the deformational features affecting the gypsum unit were probably driven by gravity and not by active thrusting as thought up to now the steeper frontal limb of the anticline promoted the transformation of gypsum slides into debris flows and turbidite currents that deposited their load in the adjacent deeper basin this gravitational deformation was sealed by postevaporitic upper messinian lagomare deposits the sedimentary history of the vena del gesso basin suggests that the messinian salinity crisis in the apennine foredeep as well as in the balearic tyrrhenian sicily and eastern mediterranean basins was tightly linked to tectonic processes the large scale postdepositional collapse of primary evaporitic deposits is a widespread feature in the mediterranean basins and it may have altered the original stratigraphic relationships in some places this finding has potentially important implications for a correct paleoenvironmental reconstruction of the onset of the messinian salinity crisis

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

the importance of recycling processes in the middle miocene badenian evaporite basin carpathian foredeep palaeoenvironmental implications the middle miocene badenian evaporitic succession within the carpathian foredeep poland has been conventionally described as formed in a purely marine basin until recently data from this basin have been used to deduce the sulphate isotopic composition of the ocean during the miocene and to describe evolution of major elements in seawater this paper presents a new interpretation proving major continental inputs and ongoing recycling processes it is based on detailed petrographical mineralogical studies x ray microanalysis of primary fluid inclusions in halite cryo scanning electron microscopy sem energy dispersive microanalysis eds isotopic analysis y 34 s and y 18 o in sulphates and computerbased evaporation models two boreholes wojnicz intersecting the halite succession in the centre of the basin and

petrogenesis of late cretaceous lava flows from a ceno tethyan island arc the raskoh arc balochistan pakistan abstract the raskoh arc is about 250 km long 40 km wide and trends in an ene direction the oldest rock unit in the raskoh arc is an accretionary complex early to late jurassic which is followed in age by kuchakki volcanic group the most wide spread unit of the raskoh arc the volcanic group is mainly composed of basaltic to andesitic lava flows and volcaniclastics including agglomerate volcanic conglomerate breccia and tuff with subordinate shale sandstone limestone and chert the flows generally form 3 15 m thick lenticular bodies but rarely reach up to 300 m they are mainly basaltic andesites with minor basalts and andesites the main textures exhibited by these rocks are hypocrystalline porphyritic subcumulophyric and intergranular the phenocrysts comprise mainly plagioclase an 30 54 in nok chah and an 56 64 in bunap they are embedded in a micro cryptocrystalline groundmass having the same minerals apatite magnetite titanomagnetite and hematite occur as accessory minerals major trace and rare earth elements suggest that the volcanics are oceanic island arc tholeiites their low mg 42 56 and higher feo total mgo 1 24 2 67 ratios indicate that the parent magma of these rocks was not directly derived from a mantle source but fractionated in an upper level magma chamber the trace element patterns show enrichment in lile and depletion in hfse relative to n morb their primordial mantle normalized trace element patterns show marked negative nb anomalies with positive spikes on k ba and sr which confirm their island arc signatures slightly depleted lree to flat chondrite normalized ree patterns further support this interpretation the zr versus zr y and cr versus y studies show that their parent magma was generated by 20 30 melting of a depleted mantle source the trace elements ratios including zr y 1 73 3 10 ti zr 81 59 101 83 ti v 12 39 30 34 la yb n 0 74 2 69 ta yb 0 02 0 05 and th yb 0 11 0 75 of the volcanics are more consistent with oceanic island arcs rather than continental margin arcs it is suggested that the raskoh arc is an oceanic island arc which formed due to the intra oceanic convergence in the ceno tethys during the late cretaceous rather than constructed on the southern continental margin of the afghan block as claimed by previous workers it is further suggested that the semail zagros chagai raskoh muslim bagh and waziristan island arcs were developed in a single but segmented cretaceous ceno tethyan convergence zone

origin and age of the mediterranean messinian evaporites implications from sr isotopes strontium isotope ratios from the messinian late miocene 6 4 to 4 85 ma evaporites of the mediterranean basin 1 2 support a subdivision into stratigraphically lower predominantly marine deposits lower evaporites lev lower gypsum and main salt characterized by sr isotopic ratios generally equivalent to those of messinian seawater and stratigraphically higher deposits upper evaporites uev with 87sr 86sr ratios lower than messinian seawater the range of 87sr 86sr ratios of the lev unit from the eastern mediterranean overlap with values obtained from essentially coeval red sea evaporites 3 strontium isotopic ratios measured from the upper evaporites however are lower and a high proportion of this sr was probably derived from low 87sr 86sr continental runoff that characterizes much of this basin 4 these results therefore strongly support depositional models utilizing a deep desiccated basin 1 with a constant marine inflow during the early stages including salt formation followed by a series of long lasting and sometimes isolated desiccation events that produced a strong but variable continental influence on the sr isotopic compositions of the uev strontium isotopic measurements can also be used to asses the actual timing of the deposition of the lev ratios obtained from oyster fragments and foraminifers from pre evaporitic units at odp site 654 tyrrhenian sea suggest that the major rifting phase in this region occurred between 8 and 6 5 ma ratios obtained from the early lev from the mediterranean sea suggest that initiation of evaporite deposition began about 5 65 ma ago results from units immediately overlying the uev in sicily suggest termination of evaporite deposition about 4 9 ma ago errors associated with these age estimates are about 0 5 ma 2

the mediterranean messinian salinity crisis an apennine foredeep perspective abstract owing to its expanded stratigraphic sections the apennine thrust belt offers the opportunity to better understand the evaporitic and post evaporitic messinian events a physical stratigraphic framework of messinian deposits based on facies analysis and basin wide correlation of key surfaces and sedimentary cycles is presented it is shown that the messinian apennine foredeep had marginal basins with shallow water primary evaporites and deeper basins where resedimented evaporites accumulated under relatively deep water conditions like many other mediterranean examples primary shallow water evaporites of apenninic marginal basins show evidence for subaerial exposure and erosion however the development of such an erosional surface does not correspond to the deposition of primary evaporites in the deepest part of the basin s here the unconformity can be traced towards the base of resedimented evaporites or to a level within them implying that the deeper basins of the apennine foredeep never underwent desiccation during the messinian salinity crisis but rather received the eroded marginal evaporites this fact usually overlooked raises important questions about the deep desiccation model of the mediterranean

the mediterranean water body in the late messinian interpreting the record from marginal basins on sicily the stratigraphic record of climatic and palaeoceanographic changes in the mediterranean during the late messinian is controversial on sicily sedimentary facies show a steady transgression suggesting that sub basins were hydrodynamically linked to a larger water body here we test this hypothesis using strontium isotope studies from messinian materials collected from a range of sites in the caltanissetta basin of central sicily the strata include a regionally regressive first cycle of early mid messinian age and a younger transgressive second cycle these cycles are separated by an inter regional unconformity which may be correlated with base level low stand in the mediterranean 87 sr 86 sr ratios for all first cycle gypsum fall within the expected global marine composition 0 70891 0 70897 all second cycle analyses fall within a grouping of significantly lower values 0 70868 0 70878 a surprisingly tight but discrepant grouping for data collected from shells of a brackish water fauna and from gypsum analyses from these different second cycle materials are statistically indistinguishable these results indicate that the strontium isotopic composition of waters from different sub basins on sicily are indistinguishable regardless of salinity during the late messinian therefore these basins must have mixed with a larger homogenized reservoir which we infer was the ancestral mediterranean thus circum mediterranean basins may indeed chart regional palaeoceanographic and climatic events by the end of messinian times the base level of the mediterranean was within the range of the world9s oceans but the water body probably had a distinctly different but internally homogeneous strontium isotopic composition

how dry was the mediterranean during the messinian salinity crisis the messinian salinity crisis msc 5 97 5 33 ma is an enigmatic episode of paleoceanographic change when kilometers thick evaporite units were deposited in the mediterranean basin it is generally accepted that during the msc interval there was a dry climate in the mediterranean region it is difficult to assess how dry the climate was during the msc because a modern analogue in size and duration is absent here we reconstruct hydrological changes in the mediterranean basin during the three main msc stages using excellently preserved biomarkers we used the hydrogen isotopic composition of the long chain n alkanes dn alkanes to reconstruct the hydrological changes on the land adjacent to the mediterranean sea additionally the d of long chain alkenones dalkenones is used to observe changes in the mediterranean sea water source the dn alkanes recorded during the deposition of primary lower gypsum stage 1 in monte tondo indicate a d of the precipitation comparable to the present day mediterranean implying a similar hydrologic regime indicated by experiments modelling the miocene pliocene transition elevated dalkenones values from halite unit stage 2 of the realmonte mine are associated with kainite and giant polygons consistent with presumably high evaporative conditions during halite deposition the dn alkanes recorded during the deposition of upper gypsum stage 3 in eraclea minoa indicate a dprecipitation typical for much drier settings similar to the red sea region the relative contribution of the different alkenones from eraclea minoa is similar to the one observed in present day marine settings suggesting that during stage 3 connections to the open ocean were likely maintained however the dalkenones records during deposition of the evaporites in eraclea minoa are similar to those synchronously registered in the black sea implying that a similar hydrologic regime characterized by extended drought covered large areas of southeastern europe based on the dalkenones similarity and the paratethys type of lago mare fauna in the mediterranean we speculate that the surface water during stage 3 was at times derived from the black sea

s and o so 4 isotopes simultaneous modeling and environmental significance of the nijar messinian gypsum spain abstract the messinian evaporites in nijar basin southeastern spain consist of coarse grained primary selenites and laminated fine grained gypsums these gypsums which are similar to those deposited in other mediterranean messinian basins have rather variable 34 s and 18 o so 4 21 to 24 for 34 s 10 to 17 for 18 o that are generally greater than the normal tertiary marine values 21 22 for 34 s and 13 for 18 o moreover the variation of 18 o so 4 is larger than that of 34 s continental input and reservoir effect did not play important roles for these isotope variations because these factors should have resulted in lower 34 s and 18 o so 4 than the normal marine values redox reactions of sulfur species in brine should have been responsible for the isotope variations to interpret the variable 34 s and 18 o so 4 we quantitatively modeled 34 s and 18 o so 4 of dissolved sulfate during redox reactions in two marine evaporative settings in sediment pores in a shallow water pan and in a free brine column in a deep water basin modeled 34 s and 18 o of dissolved sulfate during reduction of sulfate yield small variations especially for o isotopes in a shallow water pan however modeled 34 s and 18 o of dissolved sulfate during reduction and reoxidation cycling processes in a deep water basin show a progressive increase of up to 10 for both 34 s and 18 o so 4 above their normal marine values importantly the modeled pathways for the deep water basin setting are consistent with the nijar data whereas those for pore waters in shallow water pans are a poor fit to the nijar data the modeled results consistent with trace elements sr isotope data and selenite fabrics suggest that these yesares selenites have formed in deep marine brines the modeling results also demonstrate that 18 o so 4 can have larger variation than 34 s because the incorporation of water oxygen and probably dissolved free oxygen increases 18 o of the reoxidized sulfate whereas reoxidation of sulfide to sulfate decreases the total 34 s so 4 the modeled results could provide important geological implications for isotope and environment interpretations for ancient evaporites for example redox reactions of sulfur species during sulfate precipitation could modify normal marine 34 s and 18 o so 4 more efficiently than freshwater contributions and reservoir effects therefore to establish 34 s and 18 o so 4 age curves redox processes for ancient evaporites should be considered

paleoenvironmental significance of messinian post evaporitic lacustrine carbonates in the northern apennines italy the post evaporitic messinian in the northern sector of the adriatic foredeep is characterized by the occurrence of abundant terrigenous deposits which have been subdivided into two allostratigraphic units p ev1 p ev2 separated by an erosional unconformity of regional importance the p ev1 consists of basal complex of resedimented evaporites overlain by monotonous succession of mudstone siltstone alternations thin bedded turbidites with an overall coarsening and shallowing upwards trend it is possibly related to the rapid basin infill after the end of the salinity crisis the upper unit p ev2 shows in the most marginal areas a clear cyclical stacking pattern made up of three fining up sequences with fan delta conglomerates at the base of each cycle here a peculiar feature of the p ev2 deposits is the occurrence of three distinct laminated limestone horizons termed colombacci interbedded with fine grained varved mudstones these limestones are abiotic despite the occurrence of abundant ostracod assemblages lago mare fauna in the interbedding pelites and are interpreted as inorganically precipitated deposited in a relatively deep water environment possibly anoxic and related to permanent stratification of water mass events during periods of lake level maxima the combination of petrographical and geochemical observations on carbonate layers reveals that they correspond to events characterized by significant variations of environmental conditions however 18o 5 30 0 2 and 13c 9 28 1 68 signatures suggest that the precipitation of low mg calcite often occurred in a non marine environment and that meteoric water input had a considerable influence on late messinian sedimentation moreover the limestones have a uniform 87sr 86sr composition 0 70864 0 70875 in the range of other lago mare sediments from elsewhere in the mediterranean suggesting that some of the major mediterranean basins were likely interconnected during the lago mare phase a strongly reduced rate of hydrological exchange with the ocean is also possible but the possibility of marine influence during this stage is not completely excluded

estuarine lago mare fauna from the tertiary piedmont basin indicates episodic atlantic mediterranean exchange during the final stage of the mediterranean salinity crisis abstract the geochemical signature of fossils from lago mare deposits at moncucco torinese nw italy indicates a temporary marine ingression into the tertiary piedmont basin just before the miocene pliocene boundary isotope 18o 13c 87sr 86sr and trace element sr ca ba ca data from mollusk shells of multiple species and croaker otoliths indicate an upper estuarine environment with considerable seasonal variability in evaporation and freshwater input reconstructed salinities the presence of a paralic paleobiotope with thalassogenic water in the tertiary piedmont basin contradicts ideas of the mediterranean as a brackish lake fed by the paratethys during the latest stage of the mediterranean salinity crisis instead our data support previous notions of temporary atlantic mediterranean exchange during sea level highstands preceding the permanent re connection at the miocene pliocene transition the establishment of short lived and disjunct estuarine and lagoonal environments such as in the tertiary piedmont basin during marine ingressions also puts highly variable 87sr 86sr values and occurrences of shallow water benthic foraminifera in lago mare deposits of other mediterranean basins into a new perspective

sea level events in the south pacific linked with the messinian salinity crisis cores drilled through the carbonate cap of niue a mid oceanic carbonate platform in the south pacific contain an unusually well resolved stratigraphic section of the latest miocene at 35 to 140 m depth below sea level intensely leached and chalky intervals associated with pronounced 18 o and 13 c depletions mark the position of dissolution unconformities representing eight episodes of eustatic falls that outstripped the local rate of subsidence we demonstrate on the basis of sr isotope chronostratigraphy that these eustatic changes are correlative with the messinian salinity crisis events in the mediterranean sea level changes of about 10 m amplitude commenced at 6 14 ma and culminated in a large sea level fall that reached at least 30 m at 5 26 ma corresponding to the miocene pliocene boundary evaluation of the sea level history reported here and the contemporaneous mediterranean events supports the model of coupling between tectonic and eustatic factors that caused the onset and demise of the salinity crisis the available evidence suggests that during messinian time glacio eustatic falls and rises are likely to have modulated the connection between the atlantic and the mediterranean and influenced the evaporite deposition and may have contributed significantly to the final phase of isolation and desiccation of the mediterranean and its subsequent refilling during the zan clean deluge

deep water clastic evaporites deposition in the messinian adriatic foredeep northern apennines italy did the mediterranean ever dry out a new genetic facies model for deep water clastic evaporites is presented based on work carried out on the messinian gessoso solfifera formation of the northern apennines during the last 15 years this model is derived from the most recent siliciclastic turbidite models and describes the downcurrent transformations of a parent flow mainly composed of gypsum clasts the model allows clearer comprehension of processes controlling the production and deposition of clastic evaporites representing the most common evaporite facies of the northern apennines and the definition of the genetic and stratigraphic relationship with primary shallow water evaporites formed and preserved in marginal settings due to the severe recrystallization processes usually affecting these deposits petrographic and geochemical analyses are needed for a more accurate interpretation of the large spectrum of recognized gravity driven deposits ranging from debrisflow to low density turbidites almost all the laminar balatino gypsum previously considered a deep water primary deposit is here reinterpreted as the fine grained product of high to low density gravity flows facies associations permit the framing of the distribution of clastic evaporites into the complex tectonically controlled depositional settings of the apennine foredeep basin the messinian salinity crisis occurred during an intense phase of geodynamic reorganization of the mediterranean area that also produced the fragmentation of the former miocene apennine foredeep basin in this area primary shallow water evaporites equivalent to the mediterranean lower evaporites apparently only formed in semi closed thrust top basins like the vena del gesso basin the subsequent uplift and subaerial exposure of such basins ended the evaporite precipitation and promoted a widespread phase of collapse leading to the resedimentation of the evaporites into deeper basins vertical facies sequences of clastic evaporites can be interpreted in terms of the complex interplay between the messinian tectonic evolution of the apennine thrust belt and related exhumation erosional processes the facies model here proposed could be helpful also for better comprehension of other different depositional and geodynamic contexts the importance of clastic evaporites deposits has been overlooked in the study of other mediterranean areas based on the apennine basins experience it is suggested here that evaporites diffused into the deeper portions of the mediterranean basin may consist mainly of deep water resedimented deposits rather than shallow water to supratidal primary evaporites indicative of a complete basin desiccation