Late Tortonian-early Messinian Research Articles

Upper Miocene deposits at the southern margin of the Guadalquivir Foreland Basin (central Betic Cordillera, S. Spain). Implications for the closure timing of the Atlantic-Mediterranean connections

Mixed siliciclastic-carbonate deposits accumulated in several satellite sub-basins at the southern margin of the Guadalquivir Basin, the foreland basin of the Betic Cordillera (S. Spain). The prevailing coarse-grained sediments and deposition in shallow-water settings make it difficult to establish the precise age of the complete successions. For this reason, in previous studies, these deposits were attributed to the late Tortonian, although a Messinian age was not totally ruled out. The age of the upper Miocene deposits in the central part of the Guadalquivir Basin is here re-evaluated based on the analysis of several sections distributed in different areas: Antequera, Iznájar-Cuevas de San Marcos, Teba, and Bobadilla Estación. According to planktonic foraminifer and nannoplankton assemblages, the marine sedimentary infill of this sector of the southern margin of the Guadalquivir Basin is late Tortonian-early Messinian (late Miocene) in age. The occurrence of marine deposits characterized by the dominance of Globorotalia miotumida group, dextrally-coiled G. scitula, and the presence of G. margaritae, Globigerina multiloba, Discoaster quinqueramus, Amaurolithus primus, A. amplificus, and Reticulofenestra rotaria at the northern end of the Guadalhorce Corridor, the last active gateway in the Betic Cordillera connecting the Atlantic and the Mediterranean, indicates that it remained open until the early Messinian.

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).

Miocene paleoceanographic evolution of the Mediterranean area and carbonate production changes: A review

Miocene is a key interval in the global climate evolution as well as in the geodynamic evolution of the Mediterranean basin. Therefore, global and regional factors controlled Miocene Mediterranean oceanography, which, in turn, affected carbonate production. In this work, we review the Miocene paleocenographic evolution of the Mediterranean starting from its Sr and Nd isotope records. Secondly, we discuss Mediterranean shallow-water carbonate production changes to identify the role of oceanographic conditions in controlling carbonate systems' evolution. During Aquitanian, Sr and Nd isotope records attest an open Mediterranean, mainly fed by the Indian Ocean. From the late Burdigalian, the intermittent connection with the Indian Ocean changed the overall circulation in the basin, leading to higher residence time of waters and smaller water exchanges with the adjacent oceans. In this newly established paleoceanographic framework, regional factors such as volcanism, significantly affected Mediterranean seawater chemistry. Local tectonics led to the development of small sub-basins in the Eastern Mediterranean, characterized by restricted water exchanges from the Tortonian in the easternmost part, to the early Messinian, as attested by the deviation of the Sr isotope record of the proto-Adriatic basin. Larger Benthic Foraminifera (LBF) assemblages dominated carbonate production in the Aquitanian, while they were the most affected by the Indo-Pacific closure, showing a demise after the Burdigalian. With the LBF demise, red algae and bryozoans dominated carbonate ramps from the middle Miocene to the Tortonian. Bryozoans in particular spread during the Monterey Event, favoured by global and regional factors. During early to middle Miocene, corals formed mounds in the oligophotic zone or coral carpets controlled by local conditions. Conversely, in the late Tortonian-early Messinian, they developed as huge reef complexes in the Western and Central Mediterranean, with the exception of small restricted sub-basins, such as the proto-Adriatic basin, where red algae and small benthic foraminifera persisted.

Messinian West Alboran Sea record in the proximity of Gibraltar: Early signs of Atlantic-Mediterranean gateway restriction

Late Miocene sedimentary records in the Gibraltar arch region hold fundamental information on the Atlantic-Mediterranean connectivity before, during and after the Messinian Salinity Crisis (MSC; 5.96-5.33 Ma). In this work we tackle this still unresolved problem through a detailed foraminifer-based biostratigraphy, micropaleontological and geochemical analyses of four available records (ODP 976B and DSDP 121) and boreholes (Andalucia-G1 and Alboran A1) in the West Alboran Basin (WAB). The combined use of these different analytical techniques together with new seismic stratigraphy enabled us to create a new and revised Upper Tortonian-Lower Pliocene Alboran Sea chronostratigraphic framework and estimate the magnitude of the Zanclean erosion. At Site 976, the dominance of a peculiar cold planktonic foraminifer fauna in the late Tortonian-early Messinian could possibly imply the existence of a proto-Gibraltar Strait, while at ~7.2 Ma, changes towards warmer foraminifer assemblages, increasingly stratified water column and sharp increase in terrestrial input indicate the beginning of the restriction of the Mediterranean from the Atlantic Ocean. Cyclical changes visible both in the elemental composition and foraminifer assemblages from here onward highlight a strong precessional cyclicity, which can be correlated to the first signs of reduced ventilation and sapropel deposition in the Eastern Mediterranean. The integration of seismic profiles and core analyses finally revealed that the Messinian expression in the Alboran basin is limited to two units: one hemipelagic and one chaotic, most probably connected to the MSC final stages. The Messinian succession in the Alboran basin is topped by an unconformity, most likely related with the Zanclean reflooding, which eroded a sedimentary succession of ~1.67 Ma. An extremely rare phosphate (canaphite) and Mg rich minerals were recognized described and associated to interstitial fluids and diagenetic processes.

Late Miocene evaporite geochemistry of Lorca and Fortuna basins (Eastern Betics, SE Spain): Evidence of restriction and continentalization

AbstractThe Lorca and Fortuna basins are two intramontane Neogene basins located in the eastern Betic Cordillera (SE Spain). During the Late Tortonian—Early Messinian, marine and continental evaporites precipitated in these basins as a consequence of increased marine restriction and isolation. Here we show a stratigraphic correlation between the evaporite records of these basins based on geochemical indicators. We use SO4 isotope compositions and Sr isotopic ratios in gypsum, and halite Br contents to characterize these units and to identify the marine or continental source of the waters feeding the evaporite basins. In addition, we review the available chronological information used to date these evaporites in Lorca (La Serrata Fm), including a thick saline deposit, that we correlate with the First Evaporitic Group in Fortuna (Los Baños Fm). This correlation is also supported by micropalaeontological data, giving a Late Tortonian age for this sequence. The Second Evaporitic Group, (Chicamo Fm), and the Third Evaporitic Group (Rambla Salada Fm) developed only in Fortuna during the Messinian. According to the palaeogeographical scheme presented here, the evaporites of the Lorca and Fortuna basins were formed during the Late Tortonian—Early Messinian, close to the Betic Seaway closure. Sulphate isotope compositions and Sr isotopic ratios of the Ribera Gypsum Mb, at the base of the Rambla Salada Fm (Fortuna basin), match those of the Late Messinian selenite gypsum beds in San Miguel de Salinas, in the near Bajo Segura basin (40 km to the East), and other Messinian Salinity Crisis gypsum deposits in the Mediterranean. According to these geochemical indicators and the uncertainty of the chronology of this unit, the assignment of the Rambla Salada Fm to the MSC cannot be ruled out.

Heterozoan carbonate deposition on a steep basement escarpment (Late Miocene, Almería, south‐east Spain)

AbstractHeterozoan temperate‐water carbonates mixed with varying amounts of terrigenous grains and muddy matrix (Azagador limestone) accumulated on and at the toe of an inherited escarpment during the late Tortonian–early Messinian (late Miocene) at the western margin of the Almería–Níjar Basin in south‐east Spain. The escarpment was the eastern end of an uplifting antiform created by compressive folding of Triassic rocks of the Betic basement. Channelized coralline‐algal/bryozoan rudstone to coarse‐grained packstone, together with matrix‐supported conglomerate, are the dominant lithofacies in the higher outcrops, comprising the deposits on the slope. These sediments mainly fill small canyon‐shaped, half‐graben depressions formed by normal faults active before, during and after carbonate sedimentation. Roughly bedded and roughly laminated coralline‐algal/bryozoan rudstone to coarse‐grained packstone are the main lithofacies forming an apron of four small (kilometre‐scale) lobes at the toe of the south‐eastern side of the escarpment (Almería area). Channelized and roughly bedded coralline‐algal/bryozoan rudstone to coarse‐grained packstone, conglomerates, packstone and sandy silt accumulated in a small channel‐lobe system at the toe of the north‐eastern side of the escarpment (Las Balsas area). Carbonate particles and terrigenous grains were sourced from shallow‐water settings and displaced downslope by sediment density flows that preferentially followed the canyon‐shaped depressions. Roughly laminated rudstone to packstone formed by grain flows on the initially very steep slope, whereas the rest of the carbonate lithofacies were deposited by high‐density turbidite currents. The steep escarpment and related break‐in‐slope at the toe favoured hydraulic jumps and the subsequent deposition of coarse‐grained, low‐transport efficiency skeletal‐dominated sediment in the apron lobes. Accelerated uplift of the basement caused a relative sea‐level fall resulting in the formation of outer‐ramp carbonates on the apron lobes, which were in turn overlain by lower Messinian coral reefs. The Almería example is the first known ‘base of slope’ apron within temperate‐water carbonate systems.

The Miocene successions of the Fiora Hills: considerations about the development of the minor basins of Southern Tuscany

The Miocene sequences of Southern Tuscany represent the first post-nappe sedimentary record of the Northern Apennines, and are linked with the opening of the Tyrrhenian Sea. The sequences are located in several basins, characterizing the hinterland of the orogen. They are settled on a stack that is composed of deformed tectonic units and are capped by Plio-Pleistocene deposits. The respective basins have been strongly controlled by tectonics, which have remarkably forced the sedimentation. The Fiora Hills represent the southernmost area of Tuscany, where there are some minor but significant examples of these basins. In particular, they are the Fiora and the Tafone basins, the infillings of which are characterized by Miocene successions subdivided into several depositional units separated by unconformity or correlative conformity surfaces. This study deals with the stratigraphic features of such Miocene basinal infillings, with the aim being to define the depositional architecture and the tectonic-sedimentation interplays. Moreover, the collected data also enables there to be a discussion of some of the aspects of the basins’ structuring that are linked with the Miocene evolution of the hinterland of the Northern Apennines. The entire Miocene succession of the Fiora Hills spans from the Langhian up to the late Messinian, with there being minor differences between the Fiora-Tafone basins and with the nearby Albegna Basin. In general, we recognize: the basal Ponsano P Unit (middle Miocene), which is referable to coastal-shallow marine environment; the Lignitiferous T Unit (late Tortonian-early Messinian), which is referable to fan-delta and lacustrine systems; the Acquabona-Spicchiaiola M1 Unit (early Messinian), which is referable to lagoonal fan-deltaic environment; the Castelnuovo M2 Unit (early Messinian), which is referable to shallow marine environment; and the “Lago-Mare” M3 Unit (late Messinian), which is referable to fan-deltaic lacustrine systems. The Miocene succession is overlaid by Plio-Pleistocene marine to continental succession. The Miocene basins have settled on deformed Ligurian allochthonous units, which are markedly structured in tectonic depressions and highs and coherently so with the “crustal lateral segmentation” model. The development of the Miocene sedimentation in this sector of the chain appears to be strictly connected to the tectonic evolution of the Tyrrhenian Sea rifting. The middle Miocene deposits may in fact be related to the first syn-rift shallow-marine basins, marking the beginning of the post-nappe phase. During late Tortonian-early Messinian, important lacustrine-fan-delta systems dominated in the basins and represented the development of the middle Miocene stages. They evolved during the early Messinian in lagoonal fan-deltaic systems and then in shallow-marine systems. The transition to the upper Messinian deposits is marked by a significant unconformity, which is marked locally by angularity, thus noting an intramessinian deformative episode. This characterizes the lacustrine fan-deltaic systems that are linked to the Messinian salinity crisis for the paleo-Mediterranean Sea. The stratigraphic differences between the Fiora Hills’ basins are therefore linked to the somewhat different basinal sedimentary evolution, which is connected to the development of morphological/tectonic ridges.

Inner vs. outer wedge-top depozone “sequences” in the Late Miocene (late Tortonian–early Messinian) Sicilian Foreland Basin System; new data from the Terravecchia Formation of NW Sicily

The wedge-top depozone belongs to the innermost portion of a Foreland Basin System (FBS) (DeCelles and Giles, 1996) and includes all sediments, typically coarse-grained proximal facies, that bury the active frontal part of a fold and thrust belt. The Terravecchia Formation (Flores, 1959; Schmidt Di Friedberg, 1962, 1964–1965; Catalano, 1979) is a composite lithostratigraphic unit widespread in Sicily (southern Italy) which has been recently considered (Gugliotta, 2010) as a part of the stratigraphic record of the Late Miocene (late Tortonian to early Messinian) Sicilian wedge-top depozone and represent the main object of this paper. Two end-member wedge-top “sequences” the (i) the inner wedge-top sequence (IWS) and (ii) the outer wedge-top sequence (OWS), respectively, were recognized in the Terravecchia Formation outcropping in different sectors of NW Sicily and here described and compared on the base of both their depositional and deformative pattern. The differences existing between the IWS and OWS clearly reflect the tectono-depositional evolution of sedimentary basins located at different position across the wedge-top depozone. The more coarse grained and IWS was deposited filling narrow and often oversupplied basins located in the inner sectors of the wedge-top depozone. In these basins the sedimentary evolution has been strongly controlled by a syn-sedimentary transpressional tectonics which produced, since the late Tortonian, the development of “local scale” intraformational angular unconformities. Contemporaneously, the more fine-grained OWS was deposited filling relatively wide and mainly shallow-water marine basins, probably open to major marine areas, located in a less external position of the wedge-top depozone. In these external areas during the late Tortonian–early Messinian the transpressional tectonics was active but still confined to the deeper structural layers producing long wavelength deformation and “basin-scale” unconformities. Integrating all data an alternative tectono-depositional model of the Sicilian Late Miocene Foreland Basin System has been outlined. The model here presented substantially differs from those previously known from other authors and shows a complex wedge-top depozone articulated in a “inner” and “outer” sector whose evolution has been driven by the progressive activation of deep-seated structures.

EARLY PLIOCENE BRACKISH AND FRESHWATER OSTRACODA FROM THE VALDELSA BASIN (TUSCANY, CENTRAL ITALY)

The taxonomic study of Early Pliocene ostracods from the Valdelsa Basin (Tuscany, central Italy) has been performed on 12 samples. Fifteen species, referable to eight genera, have been identified. Eight are known species (Darwinula stevensoni (Brady & Robertson), Candona ( Neglecandona ) neglecta Sars, Pseudocandona albicans (Brady), Pseudocandona cf. P. eremita (Vejdovsky), Candonopsis arida Sieber, Ilyocypris cf. I. monstrifica (Norman), Ilyocypris bradyi Sars and Mixtacandona cf. M. tabacarui Danielopol & Cvetkov. Six species are new and have been referred to the genera Cyprideis ( C. rectangularis n. sp.), Paralimnocythere ( P. dictyonalis n. sp. and P. toscana n. sp.) and Candona ( Neglecandona ) [C. (N.) dorsoreticulata n. sp., C. (N.) subtilis n. sp., C. (N.) sambucensis n. sp.]. Two species have been left in open nomenclature, due to scarcity of material and poor preservation ( Candona ( Neglecandona ) sp. and Cyclocypridinae indet.). The Early Pliocene ostracods of the Valdelsa Basin show palaeobiogeographical affinities with both the Central and Western European faunas and the Balkan candonids. The occurrence of ostracods with Balkan and Eastern Europe affinity is also known from the more ancient Italian deposits of the late Tortonian-early Messinian and latest Messinian age. In the first case, the ostracods widespread by passive dispersal, whereas during the latest Messinian they actively dispersed in the Palaeo-Mediterranean area due to its connection with the central and eastern Paratethyan domains.

An Upper Miocene siliciclastic-carbonate ramp: depositional architecture, facies distribution, and diagenetic history (Capo Vaticano area, southern Italy)

During the Late Miocene, the marginal areas of the Mediterranean Basin were characterized by the development of mixed siliciclastic-carbonate ramps. This paper deals with a temperate siliciclastic-carbonate ramp (late Tortonian–early Messinian in age) which crops out in the Capo Vaticano area, Southern Apennines (Italy). Carbonate components are mainly represented by calcitic skeletal fragments of coralline red algae, bryozoans, bivalves, and larger foraminifera, whereas corals, brachiopods, echinoderms, and planktonic foraminifera are subordinate. In the studied ramp, the depositional geometries of the main unit, the ‘Sabbie gialle ad Heterostegina’, show a gradual steepening from low/middle (dip about 2–5°) to steep slope settings (up to 25°). The microfacies observations, the quantitative analyses of the main biogenic components as well as the rhodolith shapes and growth forms allowed the differentiation between the middle and the outer ramp depositional setting and the refining of the stratigraphic framework. The middle ramp is characterized by coralline red algal debris packstone facies often associated with larger foraminiferal floatstone/packstone facies, while the outer ramp is characterized by rhodolith floatstone/rudstone facies. These facies pass basinward into typical open-marine deposits (planktonic foraminiferal facies). The taxonomic composition of the coralline red algal assemblage points to a temperate paleoclimate and emphasizes the Miocene Mediterranean phytogeographic patterns. The absence of non-skeletal grains (ooids and green algae), the paucity of Porites patch reefs, the rare occurrence of primary marine cementation, all confirm that the studied ramp was poorly lithified within a warm–temperate setting. The flat depositional profile of the ramp can be related to the absence or paucity of primary marine carbonate cements.

Late Miocene seep-carbonates and fluid migration on top of the Montepetra intrabasinal high (Northern Apennines, Italy): Relations with synsedimentary folding

During the Miocene, hydrocarbon seep-carbonates located atop intrabasinal highs and associated with sediment instability, formed commonly at the deformation front of the Northern Apennine collisional orogen. The parallelism between the structural trend and the distribution of seep-carbonates suggests a close relationship between tectonics and gas/fluid emission. The “Montepetra intrabasinal high” was formed during the closure stage of the foredeep, being related to the synsedimentary growth of an anticline. Field geometry suggests that detachment folding was the leading mechanism of anticline growth and synsedimentary instability along the anticline flanks. Ten different bodies of seep-carbonates occur in the Tortonian–early Messinian sediments: nine in the hinge zone and one in the southern backlimb of the anticline. Foraminiferal study, geochemistry, facies investigation and the three-dimensional geometry of carbonate bodies with respect to the encasing terrigenous sediments indicate a protracted (late Tortonian–early Messinian) activity of fluid migration with re-mobilization and ascent of sediments from the core of the anticline, stabilization of chemosynthesis-related communities, and in-situ brecciation. Seepage atop the intrabasinal high was fed by different circuits: one related to the compaction-dewatering of shallow (Tortonian–early Messinian) sediments, and a deeper one related to the deformation of the anticline core and to the activity of detachment surfaces and of faults propagating through the sedimentary cover.

The genus Adeonella (Bryozoa, Ascophora) in the Mediterranean, with description of two new living species and rediscovery of a fossil one

The bryozoan genus Adeonella from the Mediterranean area has been investigated. Analysis includes the two species traditionally recorded as living in this basin: Adeonella calveti Canu and Bassler and Adeonella pallasii (Heller) and the description of two new living species Adeonella pozarae sp. nov. and Adeonella flabellata sp. nov., both from the Adriatic. The fossil distribution of the former two species, going back to the Middle–Late Pliocene and the Late Tortonian–Early Messinian, respectively, has been discussed. A further fossil species Adeonella adae (Neviani), seemingly restricted to the Pleistocene of the central Mediterranean, is reported after more than one hundred years. These records, together with that of Adeonella polystomella (Reuss), already known from this area, add new insights on the history of Adeonella in the Late Cenozoic.

Micropaleontology and paleoecology of the Neogene sediments in the Adana Basin (South of Turkey)

This paper analyses the stratigraphical features and fossil associations (ostracod and planktonic foraminifer) of the late Miocene deposits in the Adana Basin. In this research, numerous samples were collected from the sediments, both below and above the Messinian evaporitic layers which cropped out in the western and middle part of the Adana Basin, due to paleoenvironmental changes during the Messinian salinity crisis. The fine-grained sediments below the gypsum layers surrounding Topçu and Karayayla villages located in the western part of the Basin are sterile. Nodular anhydrite and enterolithic structures are well developed in these selenitic gypsum layers, which are supposed to represent a sabkha environmental condition. In the middle part of the Adana Basin, some re-sediment detritic gypsum deposits cropped out around Semiramis village houses. The lithological characteristics and faunal assemblages of the sediments both below and above these evaporites are more or less similar to each other. Fossil fauna (ostracod and planktonic foraminifera) demonstrate that these sediments are not older than latest Tortonian, as suggested by the presence of Neogloboquadrina humerosa, and not younger than earliest Messinian, as suggested by the last occurrence of Globigerinoides bulloideus. Similar planktonic assemblages were found in the drill log bored east of the Adana Basin, where there was no evaporitic occurrence. Both the planktonic species and the presence of Globorotalia suterae (from 7.81 Ma to 7.24 Ma) point that also these fine granied sediments a late Tortonian-early Messinian in age. The quantity of kaolinite recorded is relatively higher in the Tortonian-early Messinian than in the late Messinian sediments. All data show that, during the latest Tortonian-earliest Messinian time interval, the area was characterised by shallow marine environments and humid climatic conditions.

The upper Tortonian–lower Messinian at Monte dei Corvi (Northern Apennines, Italy): Completing a Mediterranean reference section for the Tortonian Stage

A high-resolution integrated stratigraphy including biostratigraphy, magnetostratigraphy, tephrostratigraphy and cyclostratigraphy is presented for the upper Tortonian and lower Messinian (Upper Miocene) at Monte dei Corvi. Numerical age control comes from a combination of magnetobiostratigrapic dating and astronomical tuning, while radioisotope dating of ash layers produced less reliable ages. The deep marine succession is characterized by large-scale non-repetitive stratigraphic changes allowing the discrimination between a Lower, Brownish, Rossini and Euxinic Shale Interval. The sedimentary cycles, which occur superimposed on these large-scale changes, are related to astronomical climate forcing. Astronomical tuning of the sedimentary cycles provides not only absolute ages for biostratigraphic events, reversal boundaries and volcanic ash layers, but also for the observed non-cyclic changes. These can be linked to environmental and geodynamic changes in the Mediterranean region preceding the Messinian Salinity Crisis. The beginning of the Brownish Interval marked by tripartite cycles at 8.017 Ma coincides with tectonic re-arrangements in the Mediterranean, such as compression in the Betics and opening of the Rifian corridor. At 7.616 Ma the change to the calcareous Rossini Interval can be linked to tectonic uplift in the northern Apennines and the deepening of the Rifian corridor, while the Betic corridor became restricted coinciding with the end of evaporite deposition in the eastern Betics. The change to euxinic shales at 7.168 Ma reflects basin-wide restriction marked by diatomite and sapropel formation in the Mediterranean basin related to the severely constricted Betic and Rifian corridors. The occurrence of a tripartite construction of cycles in the euxinic shales at 6.719 Ma coincides with diatomite formation in the eastern Mediterranean, uplift and shallowing in the Northern Apennines and further constriction of the Atlantic gateways. We conclude that late Tortonian–early Messinian tectonic and environmental events occur remarkably synchronously in the Mediterranean basin and most likely result from a combination of geodynamic processes and eccentricity-controlled climatic changes. In combination with the upper Serravallian and lower Tortonian interval, which includes the formal Tortonian Global Stratotype Section and Point (GSSP), the Monte dei Corvi is the only complete section in the Mediterranean covering the entire Tortonian Stage. We therefore propose the Monte dei Corvi section as Tortonian reference section, particularly for the Mediterranean region. In addition, it may serve as a unit-stratotype for the Tortonian.

Vermetid reefs and their use as palaeobathymetric markers: New insights from the Late Miocene of the Mediterranean (Southern Italy, Crete)

Vermetids are a poorly known family of reef-building gastropods characterized by an extremely irregular growth of the shell. Vermetid reefs are known from the Badenian (Middle Miocene) to present-day and their main importance is related to their use as sea-level indicators, strictly associated to the intertidal or immediate subtidal zone. During their evolution, two different vermetid genera have been recognized as reef-builders: Petaloconchus was the major component of vermetid reefs until the Holocene when, for still unknown reasons, it was almost completely replaced by Dendropoma. In the Mediterranean Basin, Petaloconchus reefs have been frequently found in close association to Late Miocene coral bioconstructions. New finding of Petaloconchus reefs within the slope facies of the Salento Messinian reef complex (southern Italy), together with new data from late Tortonian–early Messinian reefs of Crete (Greece) provide further information on the palaeoecology of these peculiar bioconstructions. Stratigraphical and sedimentological contexts of Salento and Crete vermetid reefs have been described, together with an account of their size, shape and inner structure. Biotic (vermetids, serpulids, bryozoans and coralline algae) and abiotic components (early marine cements and intra-reef sediment) have been identified by microfacies analysis, and their percentage-abundance has been reported. These data allow the description of vermetid reefs from two different depositional settings: along the shelf edge and, for the first time, within the coral reef slope. Shelf-edge and slope Petaloconchus reefs show the same inner structure and composition, but they differ by their shape, by the density of the framework, and by the relative proportion of the associated reef-building organisms (serpulids, bryozoans and coralline algae). Additional information on their palaeobathymetric setting have been acquired from the presence of other reef-building biota ( Porites corals and Halimeda green algae) which occur in close proximity to slope vermetid reefs, together with observations on some anatomical feature of Petaloconchus shells. Results clearly indicate for Petaloconchus reefs a palaeobathymetric range spanning from the upper subtidal zone down to 30–50 m of depth. The present study confirms vermetid reefs as important tools for the reconstructions of ancient sea-level, but great attention has to be paid to the identification of the main reef-building vermetid. Actually, while a great number of present-day Dendropoma reefs can be associated to the mean sea-level, Late Miocene vermetid reefs from Salento and Crete indicate for Petaloconchus bioconstructions a wider palaeobathymetric range.

Paratethyan Ostracod immigrants in Italy during the Late Miocene

In this paper the ostracod assemblages recovered from several brackish Late Miocene Italian deposits have been analysed from a palaeobiogeographical perspective. During late Tortonian-early Messinian it is possible to recognize in Italy rich ostracod assemblages characterized by a wide contingent of taxa with central European or Mediterranean affinity, while only few brackish and freshwater ostracods show Paratethyan affinity. The recognized composition of the ostracod assemblages matches the palaeogeographic setting of the palaeo-Mediterranean/Paratethys at that moment. In fact during late Tortonian-early Messinian the palaeo-Mediterranean and Paratethysian domains were divided and, even if the connection via the present Marmara Sea-Strimon Basin was still open, the different salinity between them represented an ecological barrier, preventing faunal exchanges. Since normal aquatic migration was impossible, it must be assumed that the Paratethyan-like taxa entered the palaeo-Mediterranean area via passive dispersal by aquatic birds. On the contrary, the ostracod assemblages from the Italian Lago-Mare deposits show the absolute predominance of Paratethyan taxa, which, according to the known palaeogeographic setting during the late Messinian Lago-Mare event, could actively migrate from the Paratethys domain, colonizing the palaeo-Mediterranean, whose endemic fauna was severely impoverished by the Messinian salinity crisis and the following water dilution.

Late Miocene brackish Loxoconchidae (Crustacea, Ostracoda) from Italy

The Late Miocene Italian brackish Loxoconchidae are herein discussed and illustrated. Three genera and two subgenera have been recognized in the brackish Italian basins: Loxoconcha, Loxocorniculina, Loxoconchissa ( Loxoconchissa) and Loxoconchissa ( Loxocaspia). Taking into account the diagnostic characters of several Loxoconchidae genera, in this paper Loxocorniculina is raised at a generic rank, Loxocaspia is confirmed as a subgenus within genus Loxoconchissa and several new species are established: Loxoconchissa ( Loxoconchissa) kinoi nov. sp., Loxoconchissa ( Loxocaspia) cosentinoi nov. sp., Loxoconchissa ( Loxocaspia) nuda nov. sp., Loxoconchissa ( Loxocaspia) punctata nov. sp., Loxoconchissa ( Loxocaspia) reticulata nov. sp., Loxoconchissa ( Loxocaspia) tuberosa nov. sp. and Loxoconchissa ( Loxocaspia) velonae nov. sp. Loxocorniculina is a typical Paratethyan genus which widespread into the Palaeo-Mediterranean during the late Messinian Lago-Mare event. Loxoconchissa was known to be widespread only in the Paratethyan realm and in this paper it is signalled for the first time in the Late Tortonian-early Messinian of Italy. The palaeobiogeography of these genera is discussed and the observed continuous distribution of Loxocorniculina against the disjunct distribution of Loxoconchissa leads to suggest that this latter genus underwent a passive dispersal via aquatic birds.

Changes in coral-reef structure through the Miocene in the Mediterranean province: Adaptive versus environmental influence

Well-documented Mediterranean examples of Miocene carbonate platforms, with complete exposures from shallow-water to basinal facies, provide evidence for temporal changes in reef-building capacity of zooxanthellate corals. In pre–late Tortonian platforms, small coralgal patches and mounds occur from platform top to the toe of slope, but they did not build to sea level. In contrast, barrier reefs with unequivocal reef-crest structures that reached sea level are documented in late Tortonian–early Messinian platforms. We suggest that a change in both calcification rates and bathymetric zonation was the result of coevolution of corals and Symbiodinium zooxanthellae, coeval to global cooling and, at least at a regional scale, a geochemical change that supported widespread aragonite precipitation through the late Miocene.

Migraines—A feminine disease

Based on more than 4,500 km of new and re-processed multichannel seismic lines, high-resolution seafloor bathymetry, available well data, and basement dredge samples, we have re-evaluated the entire stratigraphy and the tectonic evolution of the Alboran and western Algerian basins. We have correlated the sediment units deposited since the beginning of the formation of the different sub-basins, and we present for the first time a coherent stratigraphy and large-scale tectonic evolution of the whole region. The results provide the information to test and refine models of the geodynamic evolution of the westernmost Mediterranean.The data analysis supports an independent evolution of the sub-basins through the latemost Oligocene and Miocene, and a common Plio-Holocene evolution. The latemost Oligocene and Miocene evolution was controlled by the evolution of the Gibraltar subduction system. The oldest sedimentary unit is restricted to the West Alboran and Malaga basins depocenter that during the latemost Oligocene and early Miocene connected to some smaller marine basins currently uplifted and located onshore on the Betics range. Later, during the middle Miocene, the Habibas and Pytheas sub-basins formed a second depocenter on the North African margin. The different sedimentary units found in both depocenters, together with their different deformation patterns, support that the West Alboran-Malaga and the Habibas-Pytheas depocenters were separated by a major tectonic boundary. The early Tortonian initial arc magmatic activity produced the formation of new areas floored by a volcanic basement by the end of the late Tortonian, when the first sedimentary units deposited in the East Alboran sub-basin, and probably during the late Tortonian-early Messinian in the South Alboran sub-basin. Extension of the back-arc setting created oceanic crust flooring the Algero Balearic Basin. The extensional formation of the westernmost Mediterranean basins ended in the latemost Miocene. The western migration of the subduction system stopped and the convergence between the African and the European tectonic plates started to dominate the tectonic evolution of the region. During the Plio-Holocene, the sub-basins did not further subside individually so that these sediments have spread out across the whole Alboran Basin. A new tectonic contractional and strike-slip fault system developed that is active nowadays.The integration of our results together with the most recent tomographic studies has been used to test and refine the existing kinematic models of the area. None of the existing models explains all our large-scale observations.

Tectono‐climatic evolution of a Neogene intramontane basin (Late Miocene Carboneras subbasin, southeast Spain): revelations from basin mapping and biofacies analysis

ABSTRACTExceptional 3‐D exposures of fault blocks forming a 5 km × 10 km clastic sediment‐starved, marine basin (Carboneras subbasin, southeast Spain) allow a test of the response of carbonate sequence stratigraphic architectures to climatic and tectonic forcing. Temperate and tropical climatic periods recorded in biofacies serve as a chronostratigraphic framework to reconstruct the status of the basin within three time‐slices (late Tortonian–early Messinian, late Messinian, Pliocene). Structural maps and isopach maps trace out the distribution of fault blocks, faults, and over time, their relative motions, propagational patterns and life times, which demonstrate a changing layout of the basin because of a rotation of the regional transtensional stress field. Progradation of early Messinian reefal systems was perpendicular to the master faults of the blocks, which were draped by condensed fore‐slope sediments. The hangingwall basins coincided with the toe‐of‐slope of the reef systems. The main phase of block faulting during the late Tortonian and earliest Messinian influenced the palaeogeography until the late Pliocene (cumulative throw < 150–240 m), whereas displacements along block bounding faults, which moved into the hangingwall, died out over time. An associated shift of the depocentres of calciturbidites, slump masses and fault scarp degradation breccias reflects 500–700 m of fault propagation into the hangingwall. The shallow‐water systems of the footwall areas were repeatedly subject to emergence and deep peripheral erosion, which imply slow net relative uplift of the footwall. In the dip‐slope settings, erosional truncations of tilted proximal deposits prevail, which indicate rotational relative uplift. Block movements were on the order of magnitude of third order sea‐level fluctuations during the late Tortonian and earliest Messinian. We suggest that this might be the reason for the common presence of offlapping geometries in early Messinian reef systems of the Betic Cordilleras. During the late Pliocene, uplift rates fell below third order rates of sea‐level variations. However, at this stage, the basin was uplifted too far to be inundated by the sea again. The evolution of the basin may serve as a model for many other extensional basins around the world.