Recent studies on end-moraine systems located in the southern side of the Alps (northern Italy) improved the knowledge on chronology and extent of mountain glaciations during the Pleistocene. The coupling of sedimentological and magnetostratigraphy analyses revealed that a first high-energy sedimentary input from the valleys occurred at about 1 Ma, during the Jaramillo subchron. This event was followed by the prominent spread of piedmont lobes at the onset of Pleistocene glaciations in the latest Early Pleistocene (MIS 22-20), when glacial deposits were abandoned at the outlet of the main Alpine valleys at Ivrea, in Brianza and in the Garda area, close to the sea coastline. The ongoing subsidence along the southern Alpine margin led to the overlaying of different glacial units and most of them can be distinguished only in drilling cores. This condition lasted till about 0.45 Ma, when a subsequent regional uplift caused the encasement of the glacial units in the former glacial units and was contemporary to the overdeepening of the terminal reaches of the valleys, where lakes took place in interglacial times. The extent of the last two main glacial advances, related to MIS 6 and the LGM, is comparable and recorded in all the end-moraine systems. Concerning the Alpine LGM, the availability of radiocarbon datings, integrated by sedimentological, geomorphological and paleobotanical analyses, revealed that the major ice tongues moved back and forward from the maximum position many times. The two-step framework can be distinguished from the westernmost systems to the Garda area. Whereas, in the eastern Southern Alps only traces of a very large glacial expansion are recognizable outside the two youngest; this maximum expansion could be related to the MIS 16, before the change in tectono-sedimentary condition at 0.45 Ma.
The Pleistocene Glaciations in the Italian Alps recorded in piedmont end-moraine systems, new insight on extent and chronology.
Giovanni Monegato
2015
Abstract
Recent studies on end-moraine systems located in the southern side of the Alps (northern Italy) improved the knowledge on chronology and extent of mountain glaciations during the Pleistocene. The coupling of sedimentological and magnetostratigraphy analyses revealed that a first high-energy sedimentary input from the valleys occurred at about 1 Ma, during the Jaramillo subchron. This event was followed by the prominent spread of piedmont lobes at the onset of Pleistocene glaciations in the latest Early Pleistocene (MIS 22-20), when glacial deposits were abandoned at the outlet of the main Alpine valleys at Ivrea, in Brianza and in the Garda area, close to the sea coastline. The ongoing subsidence along the southern Alpine margin led to the overlaying of different glacial units and most of them can be distinguished only in drilling cores. This condition lasted till about 0.45 Ma, when a subsequent regional uplift caused the encasement of the glacial units in the former glacial units and was contemporary to the overdeepening of the terminal reaches of the valleys, where lakes took place in interglacial times. The extent of the last two main glacial advances, related to MIS 6 and the LGM, is comparable and recorded in all the end-moraine systems. Concerning the Alpine LGM, the availability of radiocarbon datings, integrated by sedimentological, geomorphological and paleobotanical analyses, revealed that the major ice tongues moved back and forward from the maximum position many times. The two-step framework can be distinguished from the westernmost systems to the Garda area. Whereas, in the eastern Southern Alps only traces of a very large glacial expansion are recognizable outside the two youngest; this maximum expansion could be related to the MIS 16, before the change in tectono-sedimentary condition at 0.45 Ma.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
