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Recent studies on the genesis of sedimentary native sulfur deposits indicate diagenetic mid‐low temperature Bacterial Sulfate Reduction (BSR) as the main process, involving organic compounds (kerogen/hydrocarbons), bacterial colonies and gypsiferous rocks. In the peri‐Mediterranean area (Southern Spain, Sicily, Northern Apennines, Israel), the main sulfur accumulations are always associated with late Miocene sulfates and organic‐rich successions encompassing the Messinian salinity crisis (MSC). In particular, the Messinian successions of the Apennine‐Adriatic foreland basin system, due to a large amount of high‐resolution stratigraphic data, represent a perfect case study for understanding the diagenetic conditions controlling the development of the BSR process during sedimentary basin evolution. In this work, thermal models performed in three sub‐basins in a sector of the Northern Apennines comprised of the Sillaro and Marecchia rivers (Italy), calibrated by means of organic and inorganic geothermometers, indicate a general thermal immaturity of the studied successions attained as a result of a constant heat flow similar to the present day one (ca. 40 mW/m2) since Late Tortonian and lithostatic loads between 615 and 1,710 m depending on different sub‐basins. These results suggest that the MSC deposits experienced maximum temperatures between about 39°C and 65°C. Temperatures derived from thermal models have been used to constraint occurrence of the diagenetic BSR associated with evaporitic deposits providing thermal constraints in sulfur genesis as well as new useful thermal‐constraints for basin analysis studies. [ABSTRACT FROM AUTHOR]

The 87Sr/86Sr ratio is a proxy of the hydrologic structure of marginal basins characterized by the mixing between marine and continental waters. This reliable paleoceanographic and paleoclimatic tool is considered a key to the reconstruction of high‐amplitude hydrologic changes that governed the evolution of the Mediterranean region during the Messinian salinity crisis (MSC), when reduced connections with the global ocean resulted in the deposition of the most studied Earth's salt giant. Paleohydrological dynamics leading to the deposition of the Primary Lower Gypsum during the first stage of the MSC were revealed by the study of the 87Sr/86Sr composition of 114 samples from the Vena del Gesso basin (Northern Apennines, Italy). The analysis of seven high‐resolution 87Sr/86Sr profiles from individual gypsum beds suggests a climatic influence of precessional‐scale orbital parameters during evaporite deposition. The variations of Sr isotope ratios over time indicate that gypsum precipitation started from a seawater body dominated by continental contributions, followed by a relative increase of marine input. The overall results show a gradual upward detachment from the global ocean 87Sr/86Sr curve, with crucial steps corresponding to the most extreme eccentricity minima, suggesting an orbital influence on the hydrological balance of the basin. Given the sedimentological and geochemical analogies shared by the Mediterranean marginal basins that hosted the Primary Lower Gypsum deposition, the 87Sr/86Sr evolution of the Vena del Gesso basin may be considered as indicative of Mediterranean‐scale hydrologic dynamics, driven by gradual reduction of exchanges with the Atlantic and variable freshwater input. Key Points: High‐resolution Sr isotope data record orbitally forced climate control on basin hydrology at different time scales87Sr/86Sr profiles highlight recurrent precessional‐scale hydrological oscillationsThe stepwise divergence of the 87Sr/86Sr signal from the global ocean trend suggests gradual reduction of Mediterranean‐Atlantic exchanges [ABSTRACT FROM AUTHOR]

The Upper Gypsum unit of the Caltanissetta Basin (Sicily) records the last phase of the Messinian salinity crisis comprising the so-called ‘Lago Mare’ event. A new facies analysis study recognizes nine to ten depositional cycles consisting of seven rhythmically interbedded primary gypsum bodies, and two to three sandstone bodies separated by marly terrigenous horizons showing laterally persistent vertical organization. A basal thin gypsum bed is overlain by a cluster of five thicker gypsum bodies. A marly interval containing two distinct sandstone horizons separates this cluster from the overlying uppermost (seventh) gypsum body. The terrigenous Arenazzolo Formation, in turn followed by the lower Pliocene Trubi Formation, is considered here to form the uppermost part of the Upper Gypsum unit. The rhythmic alternation in the sandy marls and gypsum/sandstone bodies records the response of sediments from shelfal to deltaic systems to precession-driven arid-wet climate fluctuations causing cyclical changes of both base-level and water concentration. During wet climate phases (at insolation maxima) marl and sandstone were deposited in a hypohaline environment as suggested by: (i) the typical Lago Mare faunal assemblage and (ii) the negative δ18O values. During arid phases (at insolation minima) the reduced meteoric supply, recorded by higher δ18O values in the carbonate, caused the development of a negative hydrological budget leading to evaporite precipitation. At a basinal scale the Upper Gypsum unit unconformably overlies a mainly clastic evaporite unit containing carbonate breccia (the so-called ‘Calcare di Base’) and/or clastic gypsum. Towards the basin centres, where the basal contact becomes conformable, a primary gypsum cumulate horizon is present. This layer is interpreted as a possible lateral equivalent of the Halite unit present only in the deepest depocentres. Based on astronomical calibration of the depositional cycles, the Upper Gypsum unit, including the Arenazzolo Formation, spans the interval between 5·33 and 5·53 Ma. This new age calibration allows the deposition of the Halite unit to be dated between 5·6 Ma (top of the Lower Evaporites) and 5·55 Ma (base of the Upper Evaporites) corresponding to isotopic stages TG12 and/or TG14. [ABSTRACT FROM AUTHOR]

Abstract: A possible deep-water non-evaporitic unit equivalent of the Messinian Lower Evaporites has been recognised in the Northern Apennine foredeep. This unit, whose existence is implicitly admitted in the two-step model of the Mediterranean Messinian salinity crisis is documented here for the first time; it occurs throughout the Apennine foredeep basin below a thick horizon of resedimented gypsum deposits, usually ascribed to the Lower Evaporites. Actually, the Lower Evaporites of the Apennine foredeep basin include both shallow-water, in situ precipitated facies and deep-water, resedimented facies deposited in distinct depocenters. The usually envisaged coeval nature of the two deposits has been recently challenged in several works based on a) physical–stratigraphic considerations about the downbasin correlation of the Messinian erosional surface cutting on top the in situ evaporites with the sharp base of the resedimented evaporites unit and b) the common occurrence of a barren unit below the resedimented evaporites which has no obvious equivalents in pre-evaporitic successions underlying the in situ precipitated evaporites. In this work a multidisciplinary study has been carried out on a 140 m-thick composite section (Fanantello section) to definitely assess the age and palaeoenvironmental characteristics of the unit underlying the resedimented gypsum deposits. The topmost part of the section comprises a 60 m-thick succession of barren euxinic shales falling entirely within a reversed polarity chron and characterised by a) the complete disappearance of Foraminifera, b) the occurrence of high salinity tolerant thecosomatous pteropods (Creseis sp.) c) the abundance peaks of the calcareous nannofossil Sphenolithus abies (interpreted as related to highly stressed likely hyperhaline conditions), d) the appearance of hyperhaline and/or stratified water molecular indicators (gammacerane, <0.2 pristane/phytane ratio, <1 n-alkanes odd–even predominance). Based on a multidisciplinary integrated stratigraphic approach this barren interval, is here proposed to be a deeper-water time-equivalent of the in situ primary Lower Evaporites, thus allowing to assess the events connected to the onset and the first phase of the Messinian salinity crisis from a basinal perspective. These data lend support to the hypothesis that the resedimented evaporite deposits of the Apennine foredeep basin postdate the in situ evaporites, thus implying that the term Lower Evaporites actually comprises rock bodies with different origins and separated in time and space by the Messinian erosional surface and its correlative conformity. This could be true also for other Mediterranean basins where the stratigraphy of deep-water successions should be carefully re-examined. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

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, δ18O (−5.30/+0.2) and δ13C (−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. [Copyright &y& Elsevier]

Discusses the implications of sedimentary and tectonic evolution of the Vena del Gesso basin on the onset of the Messinian salinity crisis in Italy. Slop instability; Physical stratigraphy; Relationships between shallow- and deep-water settings; Postdepositional deformation of gypsum deposits related to large-scale gravitational collapse.

The Terminal Carbonate Complex (TCC) is an upper Messinian shallow-water succession characterized by abundant oolites deposits and microbial-derived carbonates mainly known from the Western Mediterranean. The importance of the TCC derives from the close relation of its deposition with the Messinian salinity crisis and from the presence of large and diversified microbialite assemblages, which represent a rare occurrence in the Cenozoic marine sedimentary record. In this paper we provide the first detailed description of a carbonate system closely comparable to the TCC located in the central Mediterranean. This succession crops out at the southern end of the Salento Platform (South-eastern Italy) and has been investigated by means of stratigraphic, sedimentary, palaeontological and Sr isotopes analyses. Special attention has been given to the microbialite facies, with a detailed textural characterization focused on the reconstruction of their depositional and palaeoenvironmental settings. The Salento Platform TCC mainly consists of oolites deposits, Porites colonization and a diversified microbialite assemblage including six different facies, which developed mostly under shallow-water, normal marine salinity and warm climatic conditions. The overall stacking pattern is given by the superposition of three main sequences, each one including lowstand, transgressive and highstand system tracts. The Salento Platform TCC is dated to the late Messinian; our microfacies and geochemical data suggest that it could have developed during the first stage of the MSC; these carbonates are in fact followed by a sharp unconformity sealed by thick breccia deposits, possibly related to the onset of the Messinian erosional surface and to the subsequent stages of the Messinian salinity crisis. • We report the presence of the Terminal Carbonate Complex in the central Mediterranean. • The Salento Platform Terminal Carbonate Complex has been dated to the late Messinian. • A depositional system made of three superimposed sequences has been recognized. • Six microbial-derived facies have been identified, their palaeoenvironment described. • The Salento TCC has been ascribed to the first stage of the Messinian salinity crisis. [ABSTRACT FROM AUTHOR]

The recognition of peculiar laminated layers atypically rich in a biogenic intrabasinal component in the mudstone intervals from the Messinian (late Miocene) Primary Lower Gypsum unit (5.97-5.60 Ma) of the Piedmont basin (NW Italy) provides information on the palaeoenvironmental evolution at precessional insolation maxima. These cyclic layers consist of irregular alternation of cm-thick grey terrigenous laminae and whitish composite packets; the latter is in turn composed of sub mm-thick wrinkled dolomite-rich laminae that alternate with terrigenous ones. Two types of layers can be distinguished: i) peloidal layers, composed of faecal pellets and irregular diatom-rich aggregates, interpreted as marine snow floccules; and ii) filament bearing layers, composed of interwoven filaments up to 150 μm across, corresponding to remains of Beggiatoa-like giant sulphide-oxidising bacteria. By comparison with present-day settings, the peloidal layers are interpreted as flocculent layers, deposited on anoxic sea bottoms, following episodes of phytoplankton bloom in the upper water column. The filament-bearing layers are considered as chemotrophic microbial mats, growing on dysaerobic sea bottoms. The uncommon preservation of both kinds of layers is the result of extensive dolomite precipitation in the shallow subsurface, induced by bacterial sulphate reduction. The laminated layers are the first reported example of a high frequency climate-driven cyclicity in the non-evaporitic portion of the Primary Lower Gypsum unit. Their stacking pattern within the mudstone intervals reflects the gradual increase of the oxygen content of bottom waters during the humid precessional hemicycle, culminating with gypsum deposition at the onset of the arid phase. [ABSTRACT FROM AUTHOR]

Abstract: The Alba succession (Tertiary Piedmont Basin, NW Italy) preserves the northernmost record of the Messinian salinity crisis (MSC) and was deposited on the southern margin of a wide wedge-top basin, related to the involvement of the Piedmont Basin in the Apennine compressional tectonics. Pre-MSC sediments consist of a cyclic succession of marine euxinic shales and calcareous marls, deposited under the influence of precession-modulated climate changes, and document the progressive restriction of the basin prior to the onset of the MSC. They are followed by the Primary Lower Gypsum unit (PLG), deposited during the first MSC stage (from 5.96 to 5.60Ma). These sediments show a clear precession-related cyclic stacking pattern and record the lateral transition from a shallow water marginal setting in the SW to a deeper one in the NE. In marginal settings, six PLG cycles are recognised, truncated by an erosional unconformity placed at the base of the post-evaporitic sediments. The lowermost five cycles are composed of massive and banded selenite beds separated by thin shale intervals. A sharp change, evidenced by the appearance of the branching selenite facies, is recorded by the 6th gypsum bed that represents a distinctive marker bed, here called Sturani key-bed, that can be mapped throughout the study area. Basinward, the lower PLG cycles are transitional to decimetre-thick carbonate-rich layers interbedded to euxinic shales, that are overlain by the Sturani key-bed. Above the marker bed, other seven PLG cycles are present. The gypsum beds form thinner bodies compared to the Sturani key-bed and are characterised by a greater amount of fine-grained terrigenous fraction, suggesting an increase of continental runoff related, in turn, to humid climate conditions at the end of the first MSC stage. PLG cycles are followed by slumped mudstones and clastic gypsum beds that correspond to the resedimented and chaotic facies (Resedimented Lower Gypsum), deposited in the Mediterranean basins during the second MSC stage (from 5.60 to 5.55Ma). They are in turn overlain by continental and brackish water facies with Lago Mare fossil assemblages, recording the final stage of the MSC. The Messinian succession of Alba provides the opportunity to reconstruct the lateral facies transition between marginal and distal settings and to shed new light on the deep water MSC sedimentary record. Moreover, the appearance of the branching selenite facies from the 6th PLG cycle upward provides a tool for properly placing the Piedmont record in the MSC chronostratigraphic framework, allowing us to investigate the influence of climate gradients on the sedimentary response to the Mediterranean salinity crisis. [Copyright &y& Elsevier]

Abstract: Two possible alternative interpretations of the claimed Zanclean age () of two historical lithostratigraphic units of the Northern Apennines, usually referred to as Late Messinian in age and recording the so called Lagomare final event of the Messinian salinity crisis (MSC), are here discussed. The wrong age attribution of the Colombacci and “tetto” Fms. is ruled out based on data from the Maccarone and other sections showing that the Colombacci-Argille Azzurre Fm. boundary is basin wide synchronous and coincident with the Miocene-Pliocene boundary as far as it has been formally defined in the Eraclea Minoa GSSP. Alternatively, the opportunity of emending the Zanclean GSSP to a stratigraphically lower horizon recording the first evidence of marine influences in the Mediterranean following the MSC peak, seems not suitable, as (1) the marine signature of uppermost Messinian deposits is weak and still controversial and (2) no significant bio- and magnetostratigraphic events, well chronologically defined and recognizable at a global scale appear to be available to such a purpose. [Copyright &y& Elsevier]