The Molise Apennine is located near the thrust zone of the central and southern apenninic arc. It is characterized by the presence of many intra-mountain basins of different dimensions (Carpino-Le Piane, Isernia, Boiano, Sessano) which are filled with huge Quaternary successions constituted by fluvial to lacustrine and volcanoclastic deposits (Brancaccio et al. 1979; Corrado et al. 1997; Di Bucci et al. 2002; Di Bucci et al. 2005; Coltorti et al. 2005; Russo Ermolli et al. 2009). It is known that the Quaternary evolution of these basins was influenced by extensional tectonics that has acted over NW-SE oriented fault systems from Middle Pleistocene (Patacca et al. 1992). This tectonics seems to be characterized by a polyphasic activity during the Late Quaternary . In fact, all along the Molise Apennine chain, paleosurfaces are frequently present, together with erosional landscapes, karst plains and alluvial plains, that are located at similar altitudes and hanging with respect to the present base level, over hundreds of meters. These flat paleosurfaces, cutting either the Meso- Cenozoic carbonatic and silico-clastic rocks or the Quaternary deposits, present a certain continuity within the Molise Apennine, and form a typical terraced landscape. In the sector located between the structural highs of Matese and Montagnola di Frosolone massifs, besides the most ancient paleosurfaces located up to 1000 meters a.s.l., at least four orders of paleosurfaces are present at lower altitudes: 1) at about 900 m; 2) at 840-800 m; 3) at 700-600 m; 4) and finally, at about or lower than 500 m a.s.l.. Even if the geomorphologic analyses confirm a certain polyphasic landscape in the Molise Apennine, only few, partially uncertain chronological data allow the evolutionary events to be scanned Just in some cases, the limbs of paleosurfaces are chronologically attributed to the Middle Pleistocene by radiometric dating of tephra layers present within fluvial-marshy successions. In particular, the fluvial-lacustrine succession that crops out at about 800 m a.s.l. near the San Massimo village, thanks to the Ar/Ar dating of tephra layers, was attributed to 1.2-1.0 Ma and 0.6 Ma, respectively, by Brancaccio et al. (1979) and Di Bucci et al. (2005). Furthermore, the top of the fluvial-lacustrine succession outcropping in the Isernia plain near the Isernia-La Pineta settlement where important faunal remains of Palaeolithic age were descovered, on the basis of Ar/Ar dating, was referred by Coltorti et al. (2005) to about 0.5 Ma. The Sessano intra-mountain basin, located 15 km northeast of Isernia, at about 700 m asl, results hanging over other near sited ? basins, located at 400-500 m a.s.l. Moreover it is localized outside of the thrust belt zone of Isernia-Boiano. The recent multidisciplinary study (Russo Ermolli et al. 2009) allowed to define the chronological constraint of the Sessano filling. The fluvial-marshy succession is dated from the end of OIS 15 to OIS 12, when the palaeoabasin was extinguished. In add, the dating of a tephra level, outcropping at the top of the succession, gave an Ar/Ar age of 437 +/-2 ky. The entire succession, after being tilted towards east, was interested by fluvial erosion and truncation that generated flat surfaces at 720-700 m a.s.l., nowadays dissected by water courses referring to a base level at about 695 m a.s.l. Moreover, these surfaces can be linked with Tyrrhenian-ward paleo-landscapes and with other paleosurfaces of the adjacent Carpino-Le Piane intramountain basin, located at about 600 m a.s.l. So, the data of Russo Ermolli et al., (2009) represent the first morphochronological marker for the Molise Apennine and, in particular, the first ante quem and post quem date that allows the ages of the Molise Apennine landscapes to be understood. On the basis of these data and the finding of some palaeolithic artifacts, the paleosurfaces located at 700-600 m a.s.l. can be ascribed to the Middle Pleistocene, to a period that spans from 437 Ka to about 300 Ka. This data allows the 840-800 m a.s.l. landscapes to be ascribed to a time period preceding 437 Ka and those located at about 500 m a.s.l. to a time period following 437 Ka. In conclusion, the described morpho-chronological constraints add important new data to the mountain building and landscape evolution in a young orogenic chain.
New morpho-chronological constraints for the Quaternary evolution of the Molise Apennine (southern Italy): a multidisciplinary approach from the Sessano intramountain basin
SCARCIGLIA, Fabio
2009-01-01
Abstract
The Molise Apennine is located near the thrust zone of the central and southern apenninic arc. It is characterized by the presence of many intra-mountain basins of different dimensions (Carpino-Le Piane, Isernia, Boiano, Sessano) which are filled with huge Quaternary successions constituted by fluvial to lacustrine and volcanoclastic deposits (Brancaccio et al. 1979; Corrado et al. 1997; Di Bucci et al. 2002; Di Bucci et al. 2005; Coltorti et al. 2005; Russo Ermolli et al. 2009). It is known that the Quaternary evolution of these basins was influenced by extensional tectonics that has acted over NW-SE oriented fault systems from Middle Pleistocene (Patacca et al. 1992). This tectonics seems to be characterized by a polyphasic activity during the Late Quaternary . In fact, all along the Molise Apennine chain, paleosurfaces are frequently present, together with erosional landscapes, karst plains and alluvial plains, that are located at similar altitudes and hanging with respect to the present base level, over hundreds of meters. These flat paleosurfaces, cutting either the Meso- Cenozoic carbonatic and silico-clastic rocks or the Quaternary deposits, present a certain continuity within the Molise Apennine, and form a typical terraced landscape. In the sector located between the structural highs of Matese and Montagnola di Frosolone massifs, besides the most ancient paleosurfaces located up to 1000 meters a.s.l., at least four orders of paleosurfaces are present at lower altitudes: 1) at about 900 m; 2) at 840-800 m; 3) at 700-600 m; 4) and finally, at about or lower than 500 m a.s.l.. Even if the geomorphologic analyses confirm a certain polyphasic landscape in the Molise Apennine, only few, partially uncertain chronological data allow the evolutionary events to be scanned Just in some cases, the limbs of paleosurfaces are chronologically attributed to the Middle Pleistocene by radiometric dating of tephra layers present within fluvial-marshy successions. In particular, the fluvial-lacustrine succession that crops out at about 800 m a.s.l. near the San Massimo village, thanks to the Ar/Ar dating of tephra layers, was attributed to 1.2-1.0 Ma and 0.6 Ma, respectively, by Brancaccio et al. (1979) and Di Bucci et al. (2005). Furthermore, the top of the fluvial-lacustrine succession outcropping in the Isernia plain near the Isernia-La Pineta settlement where important faunal remains of Palaeolithic age were descovered, on the basis of Ar/Ar dating, was referred by Coltorti et al. (2005) to about 0.5 Ma. The Sessano intra-mountain basin, located 15 km northeast of Isernia, at about 700 m asl, results hanging over other near sited ? basins, located at 400-500 m a.s.l. Moreover it is localized outside of the thrust belt zone of Isernia-Boiano. The recent multidisciplinary study (Russo Ermolli et al. 2009) allowed to define the chronological constraint of the Sessano filling. The fluvial-marshy succession is dated from the end of OIS 15 to OIS 12, when the palaeoabasin was extinguished. In add, the dating of a tephra level, outcropping at the top of the succession, gave an Ar/Ar age of 437 +/-2 ky. The entire succession, after being tilted towards east, was interested by fluvial erosion and truncation that generated flat surfaces at 720-700 m a.s.l., nowadays dissected by water courses referring to a base level at about 695 m a.s.l. Moreover, these surfaces can be linked with Tyrrhenian-ward paleo-landscapes and with other paleosurfaces of the adjacent Carpino-Le Piane intramountain basin, located at about 600 m a.s.l. So, the data of Russo Ermolli et al., (2009) represent the first morphochronological marker for the Molise Apennine and, in particular, the first ante quem and post quem date that allows the ages of the Molise Apennine landscapes to be understood. On the basis of these data and the finding of some palaeolithic artifacts, the paleosurfaces located at 700-600 m a.s.l. can be ascribed to the Middle Pleistocene, to a period that spans from 437 Ka to about 300 Ka. This data allows the 840-800 m a.s.l. landscapes to be ascribed to a time period preceding 437 Ka and those located at about 500 m a.s.l. to a time period following 437 Ka. In conclusion, the described morpho-chronological constraints add important new data to the mountain building and landscape evolution in a young orogenic chain.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
