Salinity Crisis Research Articles

High-amplitude water-level fluctuations at the end of the Mediterranean Messinian Salinity Crisis: Implications for gypsum formation, connectivity and global climate

The formation and dissolution of salt giants impacts ocean chemistry on thousand-million year timescales. Gypsum precipitation and weathering changes the oceanic calcium concentration with implications for the carbon cycle and global temperatures. However, the connectivity of salt giants with the global ocean is necessarily restricted, making the timing of Ca2+ extraction and return more uncertain. Here we reconstruct the final phase of gypsum precipitation of the Late Miocene Mediterranean Salt Giant using micropaleontology, sedimentology and 87Sr/86Sr analyses on the most complete record preserved at Eraclea Minoa on Sicily and explore its implications for global climate. Precessional gypsum-marl couplets (Upper Gypsum) characterize the last 200 kyrs (Stage 3) of the Messinian Salinity Crisis (MSC; 5.97–5.332 Ma) in both intermediate (500–1000 m) and deep (>1000 m) Mediterranean basins. The interbedded selenitic gypsum layers contain well-preserved calcareous nannofossil assemblages dominated by Reticulofenestra minuta, a marine species which tolerates stressful conditions. Marine water is also required to explain the gypsum 87Sr/86Sr data, which describe a small range of ratios (0.708704–0.708813) lower than coeval ocean water. Mass-balance calculations indicate that during gypsum precipitation, the Atlantic made up ≤20% of a Mediterranean (“Lago-Mare”) water mass dominated by low salinity discharge from large river systems and Eastern Paratethys. This suggests episodic extraction of calcium and sulfate ions from the ocean throughout MSC Stage 3. The marls commonly contain shallow (30–100 m) brackish-water ostracods of Paratethyan (Black Sea) origin. Marls with Paratethyan ostracods are also found in both marginal (<500 m) and deep Mediterranean settings. This indicates that marl-deposition was not synchronous across the basin, but that it occurred in intermediate and deep basins during base-level lowstands at insolation minima and on the shallow Mediterranean margins during insolation maxima-driven highstands. These high-amplitude base-level fluctuations exposed the evaporites to weathering, but ponded the products in the Mediterranean basin until reconnection occurred at the beginning of the Pliocene.

Karstic geomorphology of carbonate Ouarsenis Piedmont (Boukadir region, Chelif) in Algeria: The role of the Messinian Salinity Crisis

Algeria displays various karst landscapes due to its diversity in lithology, relief, age and climate. On 16th June 1988, in the northwest of Algeria, a 60 m wide sudden collapse occurred in the Chelif Basin about 1 km north of a marginal carbonate platform. Despite this large event and visible karst dissolutions in the platform, this region has not been classified among the karst areas of Algeria yet. Our study focuses on this Messinian carbonates that form the northern piedmont of the Ouarsenis Mountain range and are covered to the north by Plio-Quaternary deposits. The geological and geomorphological data that we collected reveal that the present-day karstification is limited at the outcropping surface. Present-day carbonate dissolution is impeded by the absence of a topsoil supplying CO2 and by the presence of a calcrete improving the drainage. Although dissolution at depth is generally diffuse due to the porous and friable nature of the carbonates, two factors can, on the contrary, concentrate water infiltration: the presence of a network of more or less subvertical fractures and, occasionally, at the surface, the absence of calcrete, independently of the fracturing nodes There are few ponors and sinkholes present. The endokarst is still present as evidenced by rare caves. In epikarst, solution pipes and shelter caves are prevalent. The later results from differential weathering in relation with the carbonate facies and the progressive calcrete cementation in valleys and slopes during river incision. Near valley bottom, shelters are arranged in steps like terraces. This morphology is related to base-level lowering in relation with the deformation and uplift of the Ouarsenis piedmont. Near the southern edge of the Chelif Basin, deep (>55m) karstic voids are present and associated with paleo-valley incision presently burried by Plio-Quaternary deposits. We interpreted the large 1988 collapse in relation with this paleokarst and propose that its triggering was partly induced by a lowering of the aquifers due to a deficit of precipitation. The deep paleokarst formation and the buried river incision are attributed to the low base-level during the Messinian Salinity Crisis (5.97–5.33 Ma). We evidenced an upper karstic dissolution level filled that is attributed to a per ascendum evolution of the karstic phreatic network in relation with the following Pliocene aggradation.

Late Burdigalian to early Messinian environmental and climatic evolution of the central paleo Adriatic domain from the shallow water sedimentary record (Bolognano Fm, Eastern Majella, Central Apennines)

During the Miocene, Earth's climate evolved from a prolonged phase of global warmth into a colder mode. In the same time interval, the Mediterranean area was affected by important geodynamic and oceanographic changes evolving from a wide open basin to small enclosed basins. This work aims identifying the controlling factors of the paleoadriatic basin evolution, in one of the enclosed basins of the Mediterranean analyzing the ramp succession in the eastern Majella (Central Apennines).The stratigraphic architecture of the investigated succession shows an initial regressive phase, testified by the deposition of middle to outer ramp deposits followed by a long lasting transgressive phase between late Burdigalian to Tortonian during which hemipelagic to outer ramp sediments were deposited. At the end of the Tortonian a drop in sea level caused an erosional unconformity, reworking and deposition of inner ramp sediments. The succession evolves upward to alternating bioclastic and fine laminated organic rich deposits showing a deepening upward trend interrupted by a major sea level drop linked to the Messinian Salinity Crisis. The lower Messinian portion of the succession shows high TOC values, Al and redox-sensitive trace elements correlated with laminated sediments interpreted as deposited under anoxic conditions. The lithological alternation (bioclastic and laminated deposits) of the early Messinian interval, was likely produced in an astronomically-controlled humid and arid climate fluctuation. The increase of the terrigenous fraction coincides with an increase of Al concentrations that is associated with terrestrial organic matter. The increasing terrigenous input in the sediments is related to approaching Adriatic foredeeps during the early Messinian, promoting the progressive decay of environmental conditions in the basin.

New data on the new micromammalian localities of Afoud (Aït Kandoula Basin, Morocco) at the Mio-Pliocene boundary: Biochronological, paleoecological and paleobiogeographic implications

Small mammal remains have been discovered in three new outcrops from the Afoud locality. This site is significant from a paleontological point of view because it has yielded fauna of European affinities (Castillomys, Occitanomys, Stephanomys, Eliomys, and Prolagus). The presence of two different species of Arvicanthis from the Afoud locality represents the oldest record in North Africa. The association of small mammals from the AF12-2 deposits provides an approximate view of the local environment and climate at the time of the formation of this locality. This faunal assemblage indicates a warm, temperate, semi-arid climate and an open vegetation cover of wooded savannah. Fossil assemblages documented in this paper expand our knowledge on the Late Miocene–Early Pliocene small mammal communities of the Aït Kandoula Basin. This study provides useful data for understanding the paleobiogeography of the Mediterranean region and faunal exchanges between North Africa and the Iberian Peninsula that took place before the Messinian Salinity Crisis.

Reflooding and repopulation of the Mediterranean Sea after the Messinian Salinity Crisis: Benthic foraminifera assemblages and stable isotopes of Spanish basins

Benthic foraminiferal, sedimentological, and stable isotope analyses performed on early Zanclean sediments from Alboran Basin ODP Site 976 and southern Spanish land-based sections in the Malaga, Nijar and Sorbas basins have enabled the reconstruction of Mediterranean environmental conditions immediately after the Messinian Salinity Crisis. The presence at the Miocene – Pliocene boundary of dark layers, often enriched in organic matter, suggests that the Zanclean reflooding has created water column stratification, and reduced bottom-water oxygen levels. Considering that such dark layers are recorded at both deep and marginal settings far away from the Gibraltar gateway/s, a Mediterranean-scale water-mass stratification must have occurred. This stratification could be the result of saline Atlantic waters sinking into a less saline Mediterranean Basin still under the influence of the Paratethys. Our early Zanclean benthic δ18O data show that the Mediterranean water budget was indeed less negative than at present, explaining the lower salinity of the basin. However, the Atlantic values of the benthic δ13C registered in the Alboran basin suggest that bottom-water renewal rates were quite high during the early Zanclean, preventing the reduction of δ13C at the seafloor as observed in the Messinian records. Zanclean benthic foraminiferal repopulation sequences show similarities with recovery from low-oxic episodes during sapropel deposition. These observations, paired with the gradual deepening of the basins, suggests that the Zanclean reflooding led to a progressive shift from stressed and unstable environments towards benthic associations typical of efficient circulation and bottom water ventilation.

Lingering end to a salinity crisis

Lingering end to a salinity crisis

Seismic characterization and depositional significance of the Nahr Menashe deposits: Implications for the terminal phases of the Messinian salinity crisis in the north‐east Levant Basin, offshore Lebanon

AbstractOver the last decade, there has been a resurgence of interest in the climatic and tectonic mechanisms that drove the Messinian salinity crisis (MSC) and the associated deposition of thick evaporites. The MSC represents an unprecedented palaeoceanographic change that led to a very short (ca. 640 kyr) ecological and environmental crisis. However, across the Levantine offshore basin, the sedimentological nature of the top evaporitic units and the mechanisms that controlled the transition from a hypersaline evaporitic unit to brackish deposits (final MSC stage 3) are still disputed. Here, we re‐evaluate the deposits associated with the terminal phase of the MSC, named in offshore Lebanon as the Nahr Menashe Unit (NMU). We describe the NMU seismic facies, characterize and map its internal seismic stratigraphy and provide a new interpretation of its depositional environment, which persisted during the late Messinian and then evolved through a regional reflooding event. The base of the NMU overlies semicircular depressions, randomly distributed linear marks and surface collapse features, which are indicative of a period of intense evaporite dissolution. The NMU seismic facies observed from the slope to the deep part of the basin support the interpretation of a layered salt‐evaporite‐sand depositional system subject to complex reworking, dissolution, deposition and final erosion. A drainage network of valleys and complex tributary channels incising into the top NMU shows marked erosional characteristics, which indicate a dominant southwards sediment transfer following deposition of the NMU. The drainage network was subsequently infilled by layered sediments interpreted here to represent the post‐MSC marine sediments. Our analysis adds important details regarding previous interpretations of the NMU as fluvial in origin. Specifically, the presence of subcircular, linear dissolution features coupled with mound‐like features indicates that the NMU is composed dominantly of evaporites that were subject to dissolution prior to erosion associated with the drainage network. The NMU is interpreted to represent the deposition/redeposition of a mixed evaporite‐siliciclastic succession in a shallow marine or lacustrine environment during the tilting of the offshore Lebanese basin.

Centres of endemism of Noctuidae (Lepidoptera) in the Palaearctic arid mountains: biogeographical and phylogenetic implications

The oreal fauna is connected with orographically limited non-arboreal habitats. Its chorological centres can be recognised by the high species-diversity of numerous typical genera, and by the accumulated occurrence of endemic species and/or subspecies of disjunct species. The oreal fauna is partitioned to the alpine type, as the faunal type of humid high-mountains with strong connections to the tundral zonobiome, and the xeromontane type, as the faunal type of arid high-mountains with close connections to the eremic zonobiomes. As the results of revisions of several Noctuinae genera, species groups and/or sister species were recognised and their distributions were mapped. The restricted areas of allopatric sister species, often described by us as new for science, fulfil the criteria of the “areas of endemism”. Core areas of the Palaearctic xeromontane Noctuidae, outlined by the distribution of endemic species, have been proven by the occurrence of allopatric subspecies of polytypic species, and/or by the presence of allopatric sister species. In the revised genera of Noctuidae several types of allopatric speciation have been identified based on the analysis of the areas of endemism and of vicariance patterns. As a result of these analyses, it is proved that allopatric sister species, as elementary monophyletic supraspecific units, are suitable for phylogenetic biogeographical surveys. Although the major part of the xeromontane fauna appears to be range-restricted, a considerable fraction of the species could have expanded into the steppic zonobiome due to adaptive changes of their life cycles. High diversity of cold-adapted species originated from the Sino-Himalayan mountains by passing two main filtercorridors. One track of this bifurcation was directed across the “Rhododendron-corridor” to the Holarctic taiga zone while the other one, across the “Xeromontane filter-corridor” to the mountain systems of Central and Inner Asia. This bifurcation becomes apparent from the taxonomic division of the genera, composing both of these main faunal types. Supposedly, the faunal movements of the xeromontanean species in the West Palaearctic had been shaped by the Messinian salinity crisis and, additionally, significantly influenced by the Mid-Pleistocene climatic transition which deeply transformed the zonality of the vegetation by cooling and aridisation of vast areas.

Centres of endemism of Noctuidae (Lepidoptera) in the Palaearctic arid mountains: biogeographical and phylogenetic implications

The oreal fauna is connected with orographically limited non-arboreal habitats. Its chorological centres can be recognised by the high species-diversity of numerous typical genera, and by the accumulated occurrence of endemic species and/or subspecies of disjunct species. The oreal fauna is partitioned to the alpine type, as the faunal type of humid high-mountains with strong connections to the tundral zonobiome, and the xeromontane type, as the faunal type of arid high-mountains with close connections to the eremic zonobiomes. As the results of revisions of several Noctuinae genera, species groups and/or sister species were recognised and their distributions were mapped. The restricted areas of allopatric sister species, often described by us as new for science, fulfil the criteria of the “areas of endemism”. Core areas of the Palaearctic xeromontane Noctuidae, outlined by the distribution of endemic species, have been proven by the occurrence of allopatric subspecies of polytypic species, and/or by the presence of allopatric sister species. In the revised genera of Noctuidae several types of allopatric speciation have been identified based on the analysis of the areas of endemism and of vicariance patterns. As a result of these analyses, it is proved that allopatric sister species, as elementary monophyletic supraspecific units, are suitable for phylogenetic biogeographical surveys. Although the major part of the xeromontane fauna appears to be range-restricted, a considerable fraction of the species could have expanded into the steppic zonobiome due to adaptive changes of their life cycles. High diversity of cold-adapted species originated from the Sino-Himalayan mountains by passing two main filtercorridors. One track of this bifurcation was directed across the “Rhododendron-corridor” to the Holarctic taiga zone while the other one, across the “Xeromontane filter-corridor” to the mountain systems of Central and Inner Asia. This bifurcation becomes apparent from the taxonomic division of the genera, composing both of these main faunal types. Supposedly, the faunal movements of the xeromontanean species in the West Palaearctic had been shaped by the Messinian salinity crisis and, additionally, significantly influenced by the Mid-Pleistocene climatic transition which deeply transformed the zonality of the vegetation by cooling and aridisation of vast areas.

Diversification within an oceanic Mediterranean island: Insights from a terrestrial isopod

Understanding intra-island patterns of evolutionary divergence, including cases of cryptic diversity, is a crucial step towards deciphering speciation processes. Cyprus is an oceanic island isolated for at least 5.3 Mya from surrounding continental regions, while it remains unclear whether it was ever connected to the mainland, even during the Messinian Salinity Crisis. The terrestrial isopod species Armadillo officinalis, that is widespread across the Mediterranean, offers the opportunity to explore intra-island divergence patterns that might exhibit geographical structure related also to the region’s known paleogeography. Genome-wide ddRADseq, as well as Sanger sequencing for four mitochondrial and three nuclear loci data were generated for this purpose. In total, 71 populations from Cyprus, neighbouring continental sites, i.e., Israel, Lebanon and Turkey, and other Mediterranean regions, i.e. Greece, Italy, and Tunisia, were included in the analysis. Phylogenetic reconstructions and population structure analyses support the existence of at least six genetically discrete groups across the study area. Five of these distinct genetic clades occur on Cyprus, four of which are endemic to the island and one is widely distributed along the circum-Mediterranean countries. The sixth clade is distributed in Israel. The closest evolutionary relationship of endemic Cypriot populations is with those from Israel, while the evolutionary clade that is present in countries all around the Mediterranean is very shallow. Cladochronological analyses date the origin of the species on the island at ∼6 Mya. Estimated f4 and D statistics as well as FST values indicate the genetic isolation between the populations sampled from Cyprus and surrounding continental areas, while there is evident gene flow among populations within the island. Species delimitation and population genetic metrics support the existence of three distinct taxonomic units across the study area, two of which occur on the island and correspond to the endemic clade and the widespread circum-Mediterranean one, respectively, while the third corresponds to Israel’s clade. The islands’ paleogeographic history and recent human activities seem to have shaped current patterns of genetic diversity in this group of species.

First fossil record of Mustelus aff. punctulatus Risso, 1826: new evidence for a smooth-hound shark population in the Late Miocene North Sea Basin

Mustelus is a problematic genus in palaeoichthyology. Due to the scarcity of fossil teeth, relative homogeneity in tooth morphology and the lack of published extant dentitions, the early history of smooth-hound sharks remains poorly understood. Recently, two teeth were collected in the Tortonian Deurne Member (Diest Formation) near Antwerp (Belgium). Surprisingly, a detailed SEM-based comparison with the extant North-Eastern Atlantic species (Mustelus mustelus, Mustelus asterias, Mustelus punctulatus) allowed assigning the fossil teeth to Mustelus aff. punctulatus. Today, this species is largely restricted to the Mediterranean and lies at the very base of the placental Mustelus clade evolution. Until now, this species remained unrecognized in the existing fossil record. By (re)evaluating isolated teeth from other upper Miocene localities in the southern North Sea Basin, the existence of a widely distributed population of Mustelus aff. punctulatus for the late Serravallian and the Tortonian can now be postulated. Thereafter, the species disappeared from the North Sea. Until today, no single record of Mustelus punctulatus is known from the Mediterranean predating the Messinian Salinity Crisis. Therefore, it is hypothesized that the current populations have their origin in southward migration from northern, Atlantic populations, and this probably after the “Zanclean Flooding”.

The transition toward the Messinian evaporites identified by biomarker records in the organic-rich shales of the Tripoli Formation (Sicily, Italy)

Pre-evaporitic Messinian deposits, consisting of a cyclic alternation of diatomites with lime mudstones, and laminated marls, crop out all over the Mediterranean area, representing important archives of deteriorating environmental conditions. The peculiar section of Torrente Vaccarizzo (Sicily) shows several intervals of organic-rich shales, exceptionally high in lipid biomarkers, interbedded mostly with diatomites, laminites, and lime mudstones. This research deals with geochemical analyses of organic-rich shales to characterize the depositional environments and the organic matter source, as well as to investigate the biological archives predating the extreme saline conditions of the Messinian Salinity Crisis. The biomarker compositions with the petrographic results reflect a change from oxic/dysoxic to dysoxic/anoxic conditions towards younger strata. Although a minor terrestrial input is displayed by saccharides and angiosperm biomarkers, such as amyrins, dicarboxylic acids, and lignin degradation products, most of the n-alkanes, isoprenoids, n-alkanoic acids, steroids, hopanes, and tocopherols are produced by marine hypersaline tolerant organisms. Sulfurization of organic compounds (mainly isoprenoids and n-alkanols) complements the pyrite mineralogy also indicating anoxia. The assessment of kerogen by Rock Eval pyrolysis revealed a moderate-good oil potential and indicated thermally immature organic matter, which is also confirmed by multiple geochemical parameters (e.g. hopane, sterane). Bituminite at this stage of thermal maturity is not prone to hydrocarbon generation, but depends on the degree of bacterial alteration. This work highlights the relevance of using biomarkers to characterize the response of biological communities to deteriorating environmental conditions.

Time‐probabilistic approach to the late Miocene Messinian salinity crisis: Implications for a disconnected Paratethys

Time‐probabilistic approach to the late Miocene Messinian salinity crisis: Implications for a disconnected Paratethys

Palaeoenvironmental setting and depositional model of upper Messinian microbialites of the Salento Peninsula (Southern Italy): A central Mediterranean Terminal Carbonate Complex

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.

Taphonomic bias on calcareous micro and nannofossils and paleoenvironmental evolution across the Messinian Salinity Crisis onset: Insights from the Sorbas Basin (SE Spain)

During the Messinian Salinity Crisis (MSC, 5.97–5.33 Ma) the synergy between tectonic and climatic processes promoted the deposition of evaporites throughout the Mediterranean Basin. The disappearance of calcareous nannofossils and foraminifers at the MSC onset has been traditionally interpreted as the result of the establishment of hypersaline conditions in the water column, which were lethal for most marine eukaryotes. Here, we investigate the calcareous micro and nannofossil assemblages from the Sorbas Basin (SE Spain) spanning the onset and the first phase of the MSC (~ 5.9–5.7 Ma) in order to test whether their disappearance was related to adverse environmental conditions and/or to preferential dissolution of biogenic calcite. Micropaleontological analyses and petrographic observations suggest that the disappearance of calcareous fossils was the result of a taphonomic bias related to paleoceanographic changes that favoured the oxidation of both pyrite and organic matter at the sea floor. A poorly preserved benthic and planktic assemblage and aragonitic laminated sediment characterize the deposits of the first phase of the MSC from 5.93 Ma onward; aragonite deposition was likely bio-mediated in response to enhanced photosynthesis, as suggested by its δ13C signature. The fossil assemblage preserved in these deposits indicates a shallowing upward trend of the basin with respect to the pre-evaporitic phase, and the establishment of a lagoon-like environment characterized by episodic improvement of the connections with the open sea. We conclude that the temporary disappearance of calcareous fossils approximately at the MSC onset was related to ongoing basin restriction, which increased the sensitivity of the basin to fresh-water input and temperature changes, promoting marked fluctuations of the redox conditions in bottom sediments. This finding challenges the view of a marine biotic crisis related to hypersaline conditions at the MSC onset and opens new perspectives on the paleoenvironmental conditions that characterized this time interval.

A molecular phylogeny and phylogeography of Greek Aegean Island sand flies of the genus Phlebotomus (Diptera: Psychodidae)

The genus Phlebotomus (Diptera: Psychodidae: Phlebotominae) comprises a group of small winged insect species of medical importance. To date, ten species of Phlebotomus are known to be present in Greece; yet their evolutionary history is poorly studied due to the lack of comprehensive phylogenetic and phylogeographic studies. Herein, we aim to clarify the phylogenetic relationships amongst the local species collected from 12 Aegean Islands, Cyprus and Turkey; and to identify which of the palaeogeographic events may have influenced their biogeographic history. Our analyses revealed for the first time the presence of P. cf. major and P. sergenti in the Aegean Islands. All studied local species were retrieved as monophyletic and the mtDNA and nDNA phylogenetic trees indicated a plausible mitochondrial introgression between the closely related species of the P. major complex. From a palaeogeographic viewpoint, the major driving force that shaped the biogeographic history of the studied Phlebotomus species seems to be the dispersal that started in the Oligocene epoch, followed by several speciation events that occurred at the end of Miocene and the Plio-Pleistocene, including multiple dispersal events of Asiatic origin. The Messinian Salinity Crisis, the bimodal Mediterranean climate, and the glacial and interglacial periods were identified as key drivers for the diversification of the local species of Phlebotomus.

Plio-Quaternary sequences and tectonic events in the northern Adriatic Sea (northern Italy)

The analysis of multichannel seismic profiles and their correlation with well data in the northern Adriatic Sea (Northern Italy) has allowed to document Plio-Quaternary episodes of tectonic subsidence and uplift. They affected the sedimentation above the Mesozoic to lower Eocene Friuli-Dinaric Carbonate Platform (FDCP) and the unit composed of the Eocene Trieste Flysch and the Miocene Molassa (TFM), as well as the sedimentary succession lying SW of the FDCP. In particular, the early Zanclean reflooding that postdated the Messinian Salinity Crisis, was followed by the SW-ward progradation of a highstand to forced regressive shelf-slope system (Sequence 1). Forced regression was controlled by a main episode of tectonic uplift that occurred at the end of the Zanclean. This tectonic event also led to the formation of the sequence boundary separating the two main sequences that compose the Plio-Quaternary succession. The lower part of Sequence 2 (Piacenzian to late Pleistocene) recorded a two-step subsidence phase, which led to drowning episodes during Piacenzian and in particular late Gelasian (transgressive systems tract of Sequence 2). They were associated with the partial flooding of the TFM and the Miocene deposits overlying the FDPC, and with a downward bending of the pre-Calabrian succession toward the Apennine chain. The accommodation created during the late Gelasian drowning event was filled in part by an Alpine-sourced, SW-ward prograding system, and in part by the NE-ward paleo-Po prograding system (highstand systems tract of Sequence 2). The most recent part of Sequence 2 documents the last glacio-eustatic cycles in a physiographic context characterized by a very low gradient.

Cryptic lineages, cryptic barriers: historical seascapes and oceanic fronts drive genetic diversity in supralittoral rockpool beetles (Coleoptera: Hydraenidae)

Abstract Morphologically cryptic lineages confound many estimates of global biodiversity and are often discovered in ecologically specialized taxa, subject to strong morphological constraint. Such a situation may apply in many extreme environments, including supralittoral rockpools, where dramatic fluctuations in water availability and salinity impose strong selection pressures on the inhabitants. Here we explore the genetic diversity and phylogeography of supralittoral rockpool Ochthebius beetles in the eastern Atlantic and western Mediterranean, using a combination of mitochondrial and nuclear markers and dense geographical sampling of the three recognized widespread species. Our results point to the existence of morphologically cryptic lineages within all currently named taxa and suggest that the distribution of these is linked to both historical and contemporary marine hydrogeography; a combination of ocean currents and winds apparently driving the spatial patterns observed. The main contemporary barrier to dispersal for Ochthebius is located around the Ibiza Channel, whilst the Messinian Salinity Crisis appears to have been the ultimate driver of lineage diversification in these insects. Our results show that oceanographic processes do not just shape the evolution of fully marine species, but also impact significantly on the terrestrially derived inhabitants of the coastal zone.

Paleogeographic and sedimentary evolution of North Calabrian basins during the Messinian Salinity Crisis (South Italy)

The Rossano and Crotone basins in North Calabria represent key areas for the study of the Messinian Salinity Crisis (MSC) in the central Mediterranean. The integrated analysis of the outcropping successions coupled with well-borehole stratigraphies and seismic profiles permitted the stratigraphic and paleogeographic reconstruction of the MSC as follows:During the late Tortonian-early Messinian, open normal marine conditions typified the studied basins, as the deposition of deep-water claystones followed by diatomites (Tripoli Fm). The first basin restriction occurred during the early Messinian (5.96 Ma) when a relative sea-level still-stand triggered the formation of a carbonate platform system (Calcare di Base Fm − CdB). This latter was characterized by sabkha to shallow-water environments passing into a gentle slope to basin setting.A successive relative sea-level drop (ca. 5.60 Ma) induced a general exposure of the CdB platform systems and the creation of a marked erosional surface linkable with the Messinian Erosional Surface (MES). Consequently, progradational early LST forced regression wedges deposited and, as the reduction of open-sea connections, more severe restricted conditions took place. Later on, during the late LST, the massive deposition of salt dominated bodies brought to the sedimentary filling of the basins and to the consequent leveling of the paleobathymetric differences. Afterwards, a transgression phase (TST) inundated again the basins, causing firstly the sedimentation of clay dominated deposits, and successively, during a further sea-level still-stand (HST), the reestablishment of evaporitic conditions with deposition of widespread shallow-water sulphate deposits. Lastly, a new severe sea-level drop (LST) exposed again all the previous deposits and alluvial conglomerates deposited along incised paleovalleys above the HST sulphate deposits. This event marks the transition to the Lago-Mare phase that typifies the last stage of the MSC, before the base-Pliocene reflooding of the Mediterranean (ca. 5.33 Ma).

Multi-proxy investigation of the post-evaporitic succession of the Piedmont Basin (Pollenzo section, NW Italy): A new piece in the Stage 3 puzzle of the Messinian Salinity Crisis

Paleoenvironmental reconstruction of the Mediterranean Basin at the end of the Messinian Salinity Crisis is contentious. One section that records this final phase (Stage 3) is the Pollenzo Section in the Piedmont Basin (NW Italy). Here, we present new stratigraphic, sedimentological, petrographic, micropaleontological (ostracods, calcareous nannofossils, foraminifera, dinoflagellates) and geochemical ( 87 Sr/ 86 Sr ratios) data from the Cassano Spinola Conglomerates (CSC) and interpret the paleoenvironment of this northernmost tip of the Mediterranean Basin. The CSC comprise three depositional units: members A and C, which were deposited subaqueously, and the intervening member B, which is continental. The CSC is topped by a ~ 50 cm-thick black layer, which is directly overlain by the open marine Argille Azzurre Formation of early Zanclean age. Our investigation reveals that member A is largely barren of autochtonous microfossils, except for an almost monospecific ostracod assemblage of Cyprideis torosa at the top, which indicates shallow-water (<30 m) conditions. Paratethyan ostracods and, possibly, taxa of calcareous nannofossils adapted to low-salinity water first occur in member C. 87 Sr/ 86 Sr ratios measured on ostracod valves from the member A/B transition (0.708871–0.708870) and member C (0.708834–0.708746) are lower than the coeval Messinian seawater values (~0.709024) and the 87 Sr/ 86 Sr ratios of a hypothetical lake filling Piedmont (>0.7090) estimated by means of the present-day 87 Sr/ 86 Sr signature of the Po river, the main drainage system of Northern Italy that receives the weathering products (including ions) of the Alps and Apennines. These values are likely to reflect the mixing of local high 87 Sr/ 86 Sr river water with low 87 Sr/ 86 Sr from the Mediterranean, which at the time was dominated by inputs from Eastern Paratethys, circum-Mediterranean rivers and Atlantic Ocean. Our results suggest that, at times during the final stage of the Messinian Salinity Crisis, the Piedmont Basin was hydrologically connected with the main Mediterranean Basin. At regional scale, this implies that the water level in the Mediterranean Basin was relatively high. • Piedmont Basin alternated subaqueous and continental conditions during MSC Stage 3. • 87 Sr/ 86 Sr values are inconsistent with subaqueous sedimentation in a local river-fed endorheic lake • Piedmont Basin-Mediterranean connection during times of Paratethyan ostracods spreading. • The Mediterranean water-level was occasionally relatively high during Stage 3.