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  • 1
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    Variability in the vertical structure of the water column and paleoproductivity reconstruction in the central-western Mediterranean during the Late Pleistocene (2008)
    Elsevier
    Details
    Publication Date: 2020-12-21
    Description: A sedimentary sequence spanning Marine Isotope Stage (MIS) 6 to MIS 2 in core LC07, recovered in the central Mediterranean, has been investigated in order to produce a high-resolution paleoceanographic reconstruction. The changes in productivity deduced from calcareous plankton relative abundances and independently confirmed by the BaXS fluctuations are linked to the stability of the water column which is mainly controlled by the water mass temperature. During glacial intervals, productivity was generally enhanced. Oligotrophic and warmer water masses with a deepened seasonal thermocline can be inferred for most of MIS5. The magnetic properties of the sediment show increased occurrences of North Africa dust in the central Mediterranean during cold phases, likely as a consequence of a more efficient erosive process triggered by southward displacement of the intertropical convergence zone. Although increases in both productivity and Saharan dust occurred during cold periods, the atmospheric inputs do not seem to contribute significantly to the fertilization of primary producers. A Shannon Index curve has been used to tentatively synthesize the variations of calcareous nannofossil assemblages through the last 150 kyr. The assemblage diversity sharply increased coincident with the transition from the penultimate glacial to the last interglacial, subsequently low diversity was gradually reached again in the last glacial.
    Description: Published
    Description: 26-41
    Description: 2.2. Laboratorio di paleomagnetismo
    Description: JCR Journal
    Description: reserved
    Keywords: calcareous nannofossils ; foraminifera ; paleoproductivity ; Late Pleistocene ; central mediterranean ; 03. Hydrosphere::03.01. General::03.01.06. Paleoceanography and paleoclimatology ; 04. Solid Earth::04.04. Geology::04.04.08. Sediments: dating, processes, transport ; 04. Solid Earth::04.05. Geomagnetism::04.05.07. Rock magnetism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Quaternary climatic control of biogenic magnetite production and eolian dust input in cores from the Mediterranean Sea (2008)
    Elsevier
    Details
    Publication Date: 2020-10-29
    Description: We report high-resolution magnetic measurements from two Mediterranean piston cores: LC07 (Sicily Strait) and LC10 (Ionian Sea). Magnetostratigraphic results and δ18O data provide age constraints for core LC07, where we investigate magnetic property variations for two age intervals (0-600 kyr and 660-1020 kyr). For core LC10, rock magnetic parameters appear to be climatically controlled and are used to derive an astronomically tuned age model for the interval between 780 and 1200 kyr. In core LC07, the dominant control on the magnetic properties appears to be glacial-interglacial variations in the concentration of biogenic magnetite. In addition, an increased contribution from high coercivity minerals (e.g. hematite and/or goethite) probably reflects an enhanced eolian input during glacial periods. Climatic control of magnetotactic bacterial populations has been previously suggested in other environments, but this is the first such report from the Mediterranean. In contrast, the rock magnetic response to Quaternary climatic variability in core LC10 seems to be better expressed by variations in the concentration of high coercivity magnetic minerals. The contrast between a dominantly detrital/eolian flux and a dominantly biogenic flux at the same time for the two Mediterranean settings might relate to the presence of an active current regime in the Sicily Strait, which might decrease delivery of an eolian component to the seafloor compared to the deep Ionian Sea.
    Description: Published
    Description: 195-209
    Description: 2.2. Laboratorio di paleomagnetismo
    Description: 3.8. Geofisica per l'ambiente
    Description: JCR Journal
    Description: reserved
    Keywords: environmental magnetism ; biogenic magnetite ; eolian dust ; glacial-interglacial cycles ; Mediterranean Sea ; 04. Solid Earth::04.05. Geomagnetism::04.05.07. Rock magnetism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
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    Inter-laboratory calibration of low-field magnetic and anhysteretic susceptibility measurements (2008)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Inter-laboratory and absolute calibrations of rock magnetic parameters are fundamental for grounding a rock magnetic database and for semi-quantitative estimates about the magnetic mineral assemblage of a natural sample. Even a dimensionless ratio, such as anhysteretic susceptibility normalized by magnetic susceptibility (Ka/K) may be biased by improper calibration of one or both of the two instruments used to measure Ka and K. In addition, the intensity of the anhysteretic remanent magnetization (ARM) of a given sample depends on the experimental process by which the remanence is imparted. We report an inter-laboratory calibration of these two key parameters, using two sets of artificial reference samples: a paramagnetic rare earth salt, Gd2O3 and a commercial "pozzolanico" cement containing oxidized magnetite with grain size of less than 0.1 m according to hysteresis properties. Using Gd2O3 the 10 Kappabridges magnetic susceptibility meters (AGICO KLY-2 or KLY-3 models) tested prove to be cross-calibrated to within 1%. On the other hand, Kappabridges provide a low-field susceptibility value that is ca. 6% lower than the tabulated value for Gd2O3, while average high-field susceptibility values measured on a range of instruments are indistinguishable from the tabulated value. Therefore, we suggest that Kappabridge values should be multiplied by 1.06 to achieve absolute calibration. Bartington Instruments magnetic susceptibility meters with MS2B sensors produce values that are 2–13% lower than Kappabridge values, with a strong dependence on sample centering within the sensor. The Ka/K ratio of ca. 11, originally obtained on discrete cement samples with a 2G Enterprises superconducting rock magnetometer and a KLY-2, is consistent with reference parameters for magnetites of grain size 〈0.1 m. On the other hand, Ka values from a 2G Enterprises magnetometer and K values from a Bartington Instruments MS2C loop sensor for u-channel and discrete cement samples, will produce average Ka/K values that are unrealistically high if not properly corrected for the nominal volume detected by the sensors for these instruments. Inter-laboratory measurements of K and Ka for standard paleomagnetic plastic cubes filled with cement indicate remarkable differences in the intensity of the newly produced ARMs (with a standard deviation of ca. 21%), that are significantly larger than the differences observed from the calibration of the different magnetometers employed in each laboratory. Differences in the alternating field decay rate are likely the major source of these variations, but cannot account for all the observed variability. With such large variations in experimental conditions, classical interpretation of a "King plot" of Ka versus K would imply significant differences in the determination of grain size of magnetite particles on the same material.
    Description: Published
    Description: 25-38
    Description: 2.2. Laboratorio di paleomagnetismo
    Description: JCR Journal
    Description: reserved
    Keywords: Rock magnetism ; Magnetic susceptibility ; Anhysteretic remanent magnetization ; Calibration ; Instrumentation ; Relative ; 04. Solid Earth::04.05. Geomagnetism::04.05.07. Rock magnetism ; 04. Solid Earth::04.05. Geomagnetism::04.05.08. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
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    The Messinian–early Pliocene stratigraphic record in the southern Bajo Segura Basin (Betic Cordillera, Spain): Implications for the Mediterranean salinity crisis (2008)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: The analysis of the Messinian and Pliocene stratigraphy of the southern Bajo Segura Basin (Betic Cordillera, Spain) has revealed three highstand sedimentary phases (Messinian I, Messinian II, and Pliocene) bounded by two lowstand erosional surfaces (intra-Messinian and end-Messinian unconformities). The Messinian I highstand phase is characterized by the progradation of coastal and shallow marine sandstones (La Virgen Fm) over slope and pelagic-basin marls (Torremendo Fm). After this first phase, a fall in sea level brought about the intra-Messinian unconformity, a subaerial erosional surface with local accumulations of karstic breccias and caliche-like carbonate crusts. The Messinian II highstand phase is represented by sandy beaches and muddy lagoons (Garruchal Fm) correlative with shallow marine evaporites (San Miguel Fm); this second phase records the intra-Messinian reflooding of the basin, which characterizes the salinity crisis in the marginal basins of the Mediterranean. A new sea-level fall resulted in the end-Messinian unconformity, of which the most significant feature is the presence of a broad palaeovalley, c. 200 m deep, which, along its course, completely eroded the deposits of the Messinian II phase and part of the deposits of the Messinian I phase. The Pliocene highstand phase begins with coastal and shallow marine conglomerates and sandstones (La Pedrera Fm) which fill the deep part of the above-mentioned palaeovalley. These bottom deposits evolved gradually upwards towards pelagic marls (Hurchillo Fm), over which shallow marine and coastal sandstones prograded (Rojales Fm). This third phase records the flooding of the basin at the beginning of the Pliocene, when the salinity crisis ended in the marginal basins of the Mediterranean. The combination of calcareous nannoplankton biostratigraphy and magnetostratigraphy has confirmed that both the end of the sedimentation of the Messinian I phase, as well as the two lowstand erosional surfaces (intra- and end-Messinian unconformities) and also the onset of the Pliocene phase occurred in the chron C3r (c. 5.9–5.2 Ma). Under the assumption of the classical model of a desiccated deep basin, either of the two aforementioned erosional surfaces, or even both, could be correlative with the evaporites deposited in the abyssal parts of the Mediterranean.
    Description: Published
    Description: 267-288
    Description: 2.2. Laboratorio di paleomagnetismo
    Description: JCR Journal
    Description: reserved
    Keywords: Stratigraphy ; Magnetobiostratigraphy ; Messinian ; Pliocene ; Salinity crisis ; Mediterranean region ; 04. Solid Earth::04.04. Geology::04.04.08. Sediments: dating, processes, transport ; 04. Solid Earth::04.04. Geology::04.04.10. Stratigraphy ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism ; 04. Solid Earth::04.05. Geomagnetism::04.05.07. Rock magnetism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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