The Pliocene Mediterranean infilling of the Messinian Erosional Surface: New biostratigraphic data based on calcareous nannofossils (Bajo Segura Basin, SE Spain)

The Bajo Segura Basin (eastern Betic Cordillera) is a Mediterranean marginal basin where the Messinian Erosional Surface (MES), formed during the Messinian Salinity Crisis sea-level fall, is well developed. Overlying this major discontinuity the lower Pliocene transgressive sediments record the reflooding of the Mediterranean and the return to an open marine environment, the continental shelf being rebuilt after the Messinian erosion. The stratigraphic and biostratigraphic study of seven sections allow two transgressive-regressive sequences filling the MES to be distinguished, correlated with the previously distinguished Mediterranean offshore seismic units. Ten calcareous nannofossil bioevents have been identified. The lower sequence can be dated according to nannofossil biozones NN12 to NN14 and the upper sequence by NN15 to NN16. The boundary between both lower Pliocene sedimentary sequences is dated by the First Common Occurrence (FCO) of Discoaster asymmetricus in the uppermost sediment of the lower sequence and the First Occurrence (FO) of Discoaster tamalis in the lowermost part of the upper sequence. This discontinuity can be calibrated at between 4.1 and 4.0 Ma ago

Nannoplankton and planktonic foraminifera biostratigraphy of the eastern Betics during the Tortonian (SE Spain)

The Serravallian-Tortonian boundary was a time of strong tectonic activity in the Betic Cordillera. The Early Tortonian sediments continue to be under debate because no clear fossil attributions are available. These sediments have been assigned an Early Tortonian age by indirect stratigraphic criteria or by the absence of fossil content older or younger in age. The present work documents the Les Moreres- Albatera composite section, probably the most complete section of the Tortonian age in the Betic Cordillera, despite a major time gap of about 1 Ma due to an intra-Tortonian tectonic event. The section has two limestone units at the bottom (El Castellà) and the top (Las Ventanas) and two intermediate marly units, the lower Les Moreres and the upper Galería de los Suizos divided by the Raya del Búho Conglomerate. The calcareous nannoplankton biozones from CN5b/NN7 to CN9a/NN11a (Okada & Bukry, 1980; Martini, 1971) have been identified, as have the planktonic foraminifera biozones from MMi9 to MMi12a (Lourens et al. 2004). The calcareous nannoplankton biostratigraphy has allowed the identification of a time gap that includes the upper part of the CN7/NN9 biozones to the lower part of the CN9a/NN11a (Okada &Bukry, 1980; Martini, 1971). The integrated palaeomagnetic and biostratigraphic study of Albatera section has allowed to calibrate the C4r.1r/C4n.2n chron boundary.Published321 - 3442.2. Laboratorio di paleomagnetismoN/A or not JCRrestricte

Messinian stratigraphy and biomagnetostratigraphy in the Garruchal section (Bajo Segura Basin). Implications for the Mediterranean salinity crisis

The Messinian and Pliocene stratigraphic record in the Garruchal section (Bajo Segura Basin) has been divided into three allostratigraphic units, whose timing were established through combined calcareous nannoplankton biostratigraphy and magnetostratigraphy. The T-MI Unit (late Tortonian – Messinian) recorded the pre-evaporitic marine sedimentation (pre-Messinian salinity crisis deposits). This Unit is limited at the top by the intra-Messinian unconformity, representing a subaerial erosive phase related to a first major sea-level fall. The MII Unit (late Messinian) is characterized by lagoonal sedimentation, related to the socalled Lago Mare episode of the Mediterranean. At the top of this MII Unit is located the end-Messinian unconformity, caused by a second major sea-level fall. Over this unconformity lies the P Unit (early Pliocene), represented by marine deposit which marks a transgression, and the subsequent final of the Messinian salinity crisis.Published215-2182.2. Laboratorio di paleomagnetismoN/A or not JCRreserve

The Bajo Segura Basin (SE Spain): implications for the Messinian Salinity Crisis in the Mediterranean margins

The analysis of the Messinian and Pliocene stratigraphy of the Bajo Segura Basin (a marginal basin of the western Mediterranean) has revealed three synthems deposited in a high sea-level context: T-MI (late Tortonian-Messinian), MII (Messinian), and P (early Pliocene), bounded by two lowstand erosional surfaces (intra-Messinian and end-Messinian unconformities). With respect to the salinity crisis, we propose the following series of events: 1) pre-evaporitic or pre-crisis phase (T-MI synthem); 2) first sea-level fall and subaerial exposure (intra-Messinian unconformity), possibly related to the precipitation of the Lower Evaporites; 3) syn-evaporitic phase (MII synthem), recorded both by selenitic gypsum (Upper Evaporites) as well as by lagoon deposits (Lago-Mare); 4) second sea-level fall and subaerial exposure (end-Messinian unconformity), characterized by deeply incised palaeovalleys; and 5) postevaporitic or post-crisis phase (P synthem), which coincides with the definitive restoration of open marine conditions in the basin. A combined biostratigraphic and magnetostratigraphic study revealed that all the events linked to the salinity crisis (from the end of the pre-evaporitic phase to the beginning of the post-evaporitic phase) occurred within the chron C3r (c. 5.9-5.2 Ma).Published259-2652.2. Laboratorio di paleomagnetismoN/A or not JCRreserve

The Tortonian salinity crisis in the Fortuna Basin (southeastern Spain): Stratigraphic record, tectonic scenario and chronostratigraphy

The Neogene Fortuna and Bajo Segura basins are located on the northeastern end of the Trans-Alborán Shear Zone (TASZ), on the eastern Betic cordillera. The stratigraphic study of the infilling of these basins has shown two major sedimentary discontinuities. The first one, represented by an erosive surface separating open marine marls from an overlying coastal conglomeratic unit, is linked to the onset of the activity along the TASZ, which in this area indicates the beginning of the Abanilla Thrust emplacement. In the Fortuna Basin, the Tortonian salinity crisis, registered over this older first discontinuity, was therefore related to tectonic processes of the eastern portion of the cordillera and consequently would not have an expression in the western basins. The age of the Tortonian Salinity Crisis has been established with nannofossil biostratigraphy as Latest Tortonian at a somewhat lower stratigraphic position than previously recognized. The second sedimentary discontinuity was developed in relation with the known Mediterranean-wide Messinian salinity crisis

The Tortonian salinity crisis in the Fortuna Basin (southeastern Spain): Stratigraphic record, tectonic scenario and chronostratigraphy

The Neogene Fortuna and Bajo Segura basins are located on the northeastern end of the Trans-Alborán Shear Zone (TASZ), on the eastern Betic cordillera. The stratigraphic study of the infilling of these basins has shown two major sedimentary discontinuities. The first one, represented by an erosive surface separating open marine marls from an overlying coastal conglomeratic unit, is linked to the onset of the activity along the TASZ, which in this area indicates the beginning of the Abanilla Thrust emplacement. In the Fortuna Basin, the Tortonian salinity crisis, registered over this older first discontinuity, was therefore related to tectonic processes of the eastern portion of the cordillera and consequently would not have an expression in the western basins. The age of the Tortonian Salinity Crisis has been established with nannofossil biostratigraphy as Latest Tortonian at a somewhat lower stratigraphic position than previously recognized. The second sedimentary discontinuity was developed in relation with the known Mediterranean-wide Messinian salinity crisis.Published474-4812.2. Laboratorio di paleomagnetismoJCR Journalreserve

Nannoplankton and planktonic foraminifera biostratigraphy of the eastern Betics during the Tortonian (SE Spain)

The Serravallian-Tortonian boundary was a time of strong tectonic activity in the Betic Cordillera. The Early Tortonian sediments continue to be under debate because no clear fossil attributions are available. These sediments have been assigned an Early Tortonian age by indirect stratigraphic criteria or by the absence of fossil content older or younger in age. The present work documents the Les Moreres- Albatera composite section, probably the most complete section of the Tortonian age in the Betic Cordillera, despite a major time gap of about 1 Ma due to an intra-Tortonian tectonic event. The section has two limestone units at the bottom (El Castellà) and the top (Las Ventanas) and two intermediate marly units, the lower Les Moreres and the upper Galería de los Suizos divided by the Raya del Búho Conglomerate. The calcareous nannoplankton biozones from CN5b/NN7 to CN9a/NN11a (Okada & Bukry, 1980; Martini, 1971) have been identified, as have the planktonic foraminifera biozones from MMi9 to MMi12a (Lourens et al. 2004). The calcareous nannoplankton biostratigraphy has allowed the identification of a time gap that includes the upper part of the CN7/NN9 biozones to the lower part of the CN9a/NN11a (Okada &Bukry, 1980; Martini, 1971). The integrated palaeomagnetic and biostratigraphic study of Albatera section has allowed to calibrate the C4r.1r/C4n.2n chron boundary

Messinian stratigraphy and biomagnetostratigraphy in the Garruchal section (Bajo Segura Basin). Implications for the Mediterranean salinity crisis

The Messinian and Pliocene stratigraphic record in the Garruchal section (Bajo Segura Basin) has been divided into three allostratigraphic units, whose timing were established through combined calcareous nannoplankton biostratigraphy and magnetostratigraphy. The T-MI Unit (late Tortonian – Messinian) recorded the pre-evaporitic marine sedimentation (pre-Messinian salinity crisis deposits). This Unit is limited at the top by the intra-Messinian unconformity, representing a subaerial erosive phase related to a first major sea-level fall. The MII Unit (late Messinian) is characterized by lagoonal sedimentation, related to the socalled Lago Mare episode of the Mediterranean. At the top of this MII Unit is located the end-Messinian unconformity, caused by a second major sea-level fall. Over this unconformity lies the P Unit (early Pliocene), represented by marine deposit which marks a transgression, and the subsequent final of the Messinian salinity crisis