1,721,017 research outputs found

    Paleoenvironmental significance of Middle-Upper Pleistocene alluvial and lacustrine deposits of Mercuri basin (souther Italy).

    No full text
    The late Quaternary evolution of the Mercure paleolacustrine basin (Lucanian Apennines, southern Italy) was reconstructed through a multidisciplinary approach. In particular, here are presented the results of stratigraphical, geomorphological and palynological analysis of the fluvio-lacustrine sedimentary succession, which is Middle-Upper Pleistocene in age. The Mercure paleolacustrine basin, about 50 km2 wide, is located at the Calabria-Lucania boundary. The modern valley floor lies at 300 m asl and the sorrounding mountain tops reach 2000 m to the south and 1300/1500 to the north of the basin. The reconstruction of the sedimentary succession of the Mercure basin allows the definition of three main phases of the basin filling which occurred during the Middle-Upper Pleistocene time. The first sedimentary phase (Middle Pleistocene) is characterised by alluvial facies, which grade basinward into deltaic and lacustrine deposits. The second phase of filling (Middle-Upper? Pleistocene) consists of alternating sand-silty deposits passing upward to carbonate silts. After a dissecting phase, probably occurred during the Last Glacial Period, less widespread alluvial deposition took place at the basin margin; in particular the Upper Pleistocene deposits are telescopically inset within previous valley-side perched alluvial and lacustrine terraces, preserved as hanging remnants, gently sloping basinward. Pollen analysis was performed on the carbonate silts of the second filling phase. Two outcrops of about 12 and 16 metres were sampled at Zarafa and Sorgente Mercure. They represent the slopes of lacustrine terraces whose tops is now located up to 600 m asl. On the whole, pollen spectra reveal the existence of a very luxuriant oak forest, with Carpinus and Ulmus as main secondary elements, typical of a warm-humid interglacial period. The constant presence of Zelkova in the deciduous forest and the co-existence of Abies and Fagus in the highest forested belt suggests a late-Middle Pleistocene age for this interglacial association. In particular this interglacial should correspond to IS 7 or 5. An interglacial period corresponding to stage 9 was recognised at Acerno in the Picentini massif (Munno et al., 2001). Here the forest association was not very different but the presence of Cedrus suggests an older age for this paleolake. No other exemples of stage 7 or 5 are available in southern Apennines paleolakes

    Marine terraces in the Tyrrhenian Sea margin of the Southern Apennines (Italy): new constraints on differential vertical motions from dated paleoshorelines

    Full text link
    The Neogene to Quaternary southern Apennines mountain belt is flanked to the SW by the Tyrrhenian Sea back-arc basin, which was formed since late Miocene times. Extensional tectonics related to back-arc basin formation affected the Tyrrhenian margin of the southern Apennines since the Quaternary with formation of a series of horst and graben structures. Huge amounts of existing surface, subsurface and offshore data indicate that subsidence on the order of thousands of metres affected the grabens, and remarkable flights of marine terraces are indicative of Quaternary uplift of the horst blocks. The highest and older marine terraces, Early Pleistocene in age, occur up to several hundreds of metres above the sea level. A huge number of former studies have provided fundamental data on both the outcropping (raised) and buried paleoshorelines and littoral deposits, the chronological framework for the identified relative sea level fluctuations mostly rests on local-scale relative chronology reconstructions constrained by dating that are still quite rare and sparse. Detail-scale geomorphological-geological mapping, integrated with Quaternary stratigraphy, aimed at the recognition, characterisation and dating of raised marine terraces and paleoshorelines (tidal notches, platform inner edges) has been carried out in several key areas of the southern Apennines Tyrrhenian Sea margin, from Campania, in the North, to northern Calabria, in the South. The field surveys have been carried out both in rocky coasts (where continental deposits cover and sometimes hide the paleoshorelines) and in the two main alluvial-coastal basins, namely the Campania and Sele River plains. The new geochronological data constrain the ages of several late Middle Pleistocene to Late Pleistocene sea level markers, allowing a better definition of the vertical motions in each study area. Overall, the time-space distribution of the vertical motions on the regional scale is better reconstructed, along with the framework of the Quaternary surface uplift of the southwestern slope of the southern Apennines mountain belt

    Geomorphology and GIS analysis for mapping gully erosion susceptibility in the Turbolo catchmen (Northern Calabria, Italy)

    No full text
    This work summarizes the results of a geomorphological and bivariate statistical approach to gully erosion susceptibility mapping in the Turbolo stream catchment (northern Calabria, Italy). An inventory map of gully erosion landforms of the area has been obtained by detailed field survey and air photograph interpretation. Lithology, land use, slope, aspect, plan curvature, stream power index, topographical wetness index and length-slope factor were assumed as gully erosion predisposing factors. In order to estimate and validate gully erosion susceptibility, the mapped gully areas were divided in two groups using a random partitions strategy. One group (training set) was used to prepare the susceptibility map, using a bivariate statistical analysis (Information Value method) in GIS environment, while the second group (validation set) to validate the susceptibility map, using the success and prediction rate curves. The validation results showed satisfactory agreement between the susceptibility map and the existing data on gully areas locations; therefore, over 88% of the gullies of the validation set are correctly classified falling in high and very high susceptibility areas. The susceptibility map, produced using a methodology that is easy to apply and to update, represents a useful tool for sustainable planning, conservation and protection of land from gully processes. Therefore, this methodology can be used to assess gully erosion susceptibility in other areas of Calabria, as well as in other regions, especially in the Mediterranean area, that have similar morphoclimatic features and sensitivity to concentrated erosion
    corecore