Summary. Morphologically, the NE Ligurian Alps is an asymmetric ridge very close to the Ligurian Sea, with a gentle flank in the interior (Adriatic flank) and a steep flank facing the nearby sea (Ligurian flank). As such, the NE Ligurian Alps represent a seaward escarpment. The asymmetry of the two opposite escarpment flanks were quantified in terms of slope and general morphology. Several morphometric characteristic of the seaward Ligurian flank drainage network were analyzed. In particular, among the five Ligurian rivers that drain the escarpment on the seaward flank, (i) the convex shape of the Sansobbia and the Cerusa uppermost divides, together with (ii) field evidence of the high regressive power of their channels, (iii) the highest grade of hierarchical anomaly in the organization of their ordered channels and (iv) the highest values of drainage density all indicate that these two rivers are withdrawing and the escarpment is retreating at the expense of the inland Adriatic flank. The different azimuthal patterns of the channels on both flanks of the escarpment, together with a different rock erodibility, makes the escarpment evolve in two ways at the head of the Sansobbia (SW) and Cerusa (NE) rivers. In the SW sector, the presence of weak rocks and large portions of the Adriatic rivers flowing parallel to the escarpment edge are causing a retreat via fluvial captures that, with time, will lower the edge and reduce the escarpment asymmetry. This is evidenced by the presence, within the Sansobbia basin, of windgaps and a high concentration of nearly-flat surfaces, once part of the gentler Adriatic flank and now remnants of a paleo-landscape pinched along the steeper Ligurian flank. In the NE sector, where no evident windgaps or paleo-surfaces were found, harder rocks and azimuth channels perpendicular to the edge slow the retreating processes thus preserving the escarpment asymmetry for a longer time.

Geomorphic evolution of the seaword escarpment in the NE Ligurian Alps(Italy)

FIRPO, MARCO
2007-01-01

Abstract

Summary. Morphologically, the NE Ligurian Alps is an asymmetric ridge very close to the Ligurian Sea, with a gentle flank in the interior (Adriatic flank) and a steep flank facing the nearby sea (Ligurian flank). As such, the NE Ligurian Alps represent a seaward escarpment. The asymmetry of the two opposite escarpment flanks were quantified in terms of slope and general morphology. Several morphometric characteristic of the seaward Ligurian flank drainage network were analyzed. In particular, among the five Ligurian rivers that drain the escarpment on the seaward flank, (i) the convex shape of the Sansobbia and the Cerusa uppermost divides, together with (ii) field evidence of the high regressive power of their channels, (iii) the highest grade of hierarchical anomaly in the organization of their ordered channels and (iv) the highest values of drainage density all indicate that these two rivers are withdrawing and the escarpment is retreating at the expense of the inland Adriatic flank. The different azimuthal patterns of the channels on both flanks of the escarpment, together with a different rock erodibility, makes the escarpment evolve in two ways at the head of the Sansobbia (SW) and Cerusa (NE) rivers. In the SW sector, the presence of weak rocks and large portions of the Adriatic rivers flowing parallel to the escarpment edge are causing a retreat via fluvial captures that, with time, will lower the edge and reduce the escarpment asymmetry. This is evidenced by the presence, within the Sansobbia basin, of windgaps and a high concentration of nearly-flat surfaces, once part of the gentler Adriatic flank and now remnants of a paleo-landscape pinched along the steeper Ligurian flank. In the NE sector, where no evident windgaps or paleo-surfaces were found, harder rocks and azimuth channels perpendicular to the edge slow the retreating processes thus preserving the escarpment asymmetry for a longer time.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11567/224949
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