La successione pleistocenica marina e continentale del T. Tiepido (Appennino Modenese)
The marine-continental Pleistocene section of the Tiepido River (Modenese Apennines)
Keywords:
Marine Pleistocene, Continental Pleistocene, Northern Apennines, Paleo-soilsAbstract
Along the thalweg of the Torrente Tiepido, outcrops a sedimentary succession of the Pleistocene, about 750 m thick. For the first 605 m the succession is composed of clayey-silt and sandy sediments deposited in a marine environment. For the remaining 145 m it is composed of gravels, clayey-silt sands and peaty clays from a prevalently continental environment. The age of the succession, based on the study of Foraminifera from the marine section of the series, is lower Pleistocene; the age of the continental part is between the lower Pleistocene and the Mindel-Riss interglacial. The base of the succession, not outcropping on the thalweg is composed of about 80 m of transgressive silty clays on pre-Pliocenic formations with interposing sands, sands with pebbles and fragments of shells. The age of these clays is early Pleistocene. The sedimentological characteristics, as well as the thanatocoenosis also suggest a neritic infralittoral sedimentation environment, with little energy and mostly fine, clastic sedimentation. During the Emilian stage there is a sudden transition from the type of sedimentation resulting from a neritic, infralittoral environment to that of a beach, probably coinciding with an important tectonic phase in the Apennines. A hiatus with erosion, a disconformity, interrupts the succession and the sediments which follow represent the deposits of a continental environment; this is characterized by an extremely variable sequence of sands and clays with intercalated large lenses of gravels, occurring between fine, lacustrine and swampy continental sediments with saltuary erosive phases. The sedimentation is discontinuous and is characterized by rapid accumulation and by long ·intervals of non-accumulation probably owing to climatic variations. During one of these periods, perhaps during an interglacial, the conditions for the formation of fersiallitic soil were created. The studied section is covered with angular unconformity by terraced alluvial deposits with on the top a paleosoil of the Mindel-Riss interglacial period. Finally, various structures have been found indicating recent or very recent tectonic movements owing to vertical movement and displacement with remarkable horizontal component.
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Copyright (c) 2024 Alessandro Annovi, Mauro Cremaschi, Paola Fregni, Gianfranco Gasperi (Author)
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