Detailed structural and morphotectonic surveys along the front of the Eastern Southalpine Chain (ESC) in the western Carnic Prealps and surrounding piedmont Friuli plain, show evidence of Late Pleistocene-Holocene tectonic activity. At present the ESC accommodates about 2-3 mm/y shortening (Bechtold et al., 2009) and crustal thickening and propagates towards the Friuli piedmont Plain. According the DBMI11 (Locati et al., 2011) the Carnic Prealps was affected by some M>5.5 historical earthquakes: Bellunese (1873, Imax 9-10), Bosco del Cansiglio (1936, Imax 9), Sequals (1812, Imax 7-8), Tramonti (1784, Imax 9). In order to improve the seismotectonic of the area we studied the Maniago-M. Jouf, Arba-Ragogna and Polcenigo-Montereale thrust systems by mean of morphotectonic, structural, paleosismological and stratigraphic surveys. Geophysical investigations in selected sites and the analysis of the seismic profiles (ENI-AGIP) allow us to parametrize the tectonic structures. Along the Maniago-M. Jouf system, at the Cellina valley outlet, the middle Pleistocene succession of Maniago Libero is thrust over the upper Pleistocene fan (Zanferrari et al., 2008). At the Meduna valley outlet, the study of the terrace staircase (Monegato & Poli, 2015) illustrates a long lasting deformation in four phases since the Pliocene. In particular, the deformation of the alluvial unit related to the last aggradation of the Meduna fan (30 to 11 cal ky BP) points to a cumulative slip rate of 0.6 mm/y for the Maniago thrust. The Arba-Ragogna thrust system shows morphotectonic evidence along the piedmont plain such as anomalies of the fluvial drainage and an about 3 m high tectonic scarp between Valeriano and Lestans localities. Moreover the LGM surface of the Tagliamento outwash fan is displaced of about 4 m on the tip line of the Arba-Ragogna thrust, showing a late Pleistocene to Present slip rate of about 0.2 mm/y. The Polcenigo-Montereale thrust system cuts the slope deposits interfingering with the Cellina major alluvial fan along the piedmont area of the Cansiglio-Cavallo massif: locally the deposits related to the LGM Cellina fan are displaced of about 10 m, suggesting also for this sector a recent slip rate of about 0.6 mm/y. The uplift produced a series of telescopic fans; those related to the LGM aggradation show deformation along to the faults of the thrust system.
Active tectonics at the front of the Eastern Southern Alps in the Carnic Prealps (NE Italy, Friuli)
Monegato G;
2015
Abstract
Detailed structural and morphotectonic surveys along the front of the Eastern Southalpine Chain (ESC) in the western Carnic Prealps and surrounding piedmont Friuli plain, show evidence of Late Pleistocene-Holocene tectonic activity. At present the ESC accommodates about 2-3 mm/y shortening (Bechtold et al., 2009) and crustal thickening and propagates towards the Friuli piedmont Plain. According the DBMI11 (Locati et al., 2011) the Carnic Prealps was affected by some M>5.5 historical earthquakes: Bellunese (1873, Imax 9-10), Bosco del Cansiglio (1936, Imax 9), Sequals (1812, Imax 7-8), Tramonti (1784, Imax 9). In order to improve the seismotectonic of the area we studied the Maniago-M. Jouf, Arba-Ragogna and Polcenigo-Montereale thrust systems by mean of morphotectonic, structural, paleosismological and stratigraphic surveys. Geophysical investigations in selected sites and the analysis of the seismic profiles (ENI-AGIP) allow us to parametrize the tectonic structures. Along the Maniago-M. Jouf system, at the Cellina valley outlet, the middle Pleistocene succession of Maniago Libero is thrust over the upper Pleistocene fan (Zanferrari et al., 2008). At the Meduna valley outlet, the study of the terrace staircase (Monegato & Poli, 2015) illustrates a long lasting deformation in four phases since the Pliocene. In particular, the deformation of the alluvial unit related to the last aggradation of the Meduna fan (30 to 11 cal ky BP) points to a cumulative slip rate of 0.6 mm/y for the Maniago thrust. The Arba-Ragogna thrust system shows morphotectonic evidence along the piedmont plain such as anomalies of the fluvial drainage and an about 3 m high tectonic scarp between Valeriano and Lestans localities. Moreover the LGM surface of the Tagliamento outwash fan is displaced of about 4 m on the tip line of the Arba-Ragogna thrust, showing a late Pleistocene to Present slip rate of about 0.2 mm/y. The Polcenigo-Montereale thrust system cuts the slope deposits interfingering with the Cellina major alluvial fan along the piedmont area of the Cansiglio-Cavallo massif: locally the deposits related to the LGM Cellina fan are displaced of about 10 m, suggesting also for this sector a recent slip rate of about 0.6 mm/y. The uplift produced a series of telescopic fans; those related to the LGM aggradation show deformation along to the faults of the thrust system.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
