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90 DI MAGGIO, MADONIA, VATTANO, AGNESI and MONTELEONE

may also be identified within several orogenic belts (e.g., would “passively” involve and drag up the lowered hanging
Winkler-Hermaden 1957; Adams 1985; Iwata 1987; Kennan wall laid on it.
et al. 1997; Amato & Cinque 1999; Frisch et al. 2000; Clark et More generally, the crustal shortening, thickening and con-
al. 2006; Legrain et al. 2014). In agreement with the interpre- sequent isostatic compensation affecting all zones of collision
tation of Amato & Cinque (1999) for the Campano–Lucano can explain the low rates of widespread uplift (maximum
Apennines, the relicts of the planation surfaces and their con- value 0.4 m/ky) recorded in western Sicily from south to north
nected landforms of western Sicily belong to uncompleted (Babault & Van Den Driessche 2013; Schoenbohm 2013 and
erosion cycles that had a duration of some hundred thousand references therein).
years and that occurred during the construction of the chain, The effects of the tectonic processes affecting the whole of
when the relief was located at a lower elevation, but higher western Sicily (gradual Quaternary uplift from south to north;
and far from the base-level (S coast), though the topographical sudden Emilian block-faulting to its northern side) consist of
surface was gently graded. The subsequent erosion then cut a strong asymmetry in its topographic profile, with a northern
down the surrounding areas on weak rock, leaving low-relief slope much shorter and steeper than the southern slope.
surfaces on resistant rock. In addition, these relicts remained Accordingly, the steeper northern rivers with a higher erosion
until the present-day because the Sicilian Apennines are a very power are characterized by regressive erosion and over time
recent belt, lately surfaced, and the erosion has not had enough have enlarged their catchment areas at the expense of the
time to lead to intersection of river valleys and to reach the southern river basins, through capture phenomena (see
innermost areas. inverted drainage phenomena in the head areas on the northern
In the northern end of western Sicily and after the construc- river basins). Following these processes, the regional water-
tion of an elevated relief, the important extensional tectonic shed is currently located further south than the line connecting
event that occurred during the Calabrian stage (about 1.5 Ma the highest mountain peaks of Sicily.
— Hugonie 1982) produced normal faults representing the Furthermore, the river down-cutting, uplift movements, and
peripheral effect of the back-arc extension of the Tyrrhenian extensional tectonics result in a high relief that is a major
Sea (Amato & Cinque 1999; Nigro & Renda 2005; Pepe et al. cause of the development of the surface landslides and DSGSD
2005; Caiazzo et al. 2006; Di Stefano et al. 2007; Cuffaro et al. phenomena affecting the mountain areas of northern Sicily
2011; Carminati & Doglioni 2012). These faults resulted in the (Di Maggio et al. 2014 and references therein; Agnesi et al. 2015).
displacement of the previous low-relief surfaces and the dis- Finally, as regards the timing of the geomorphological evo-
mantling, collapse, and lowering of the northernmost margin lution of Sicily it is necessary to specify the following con-
of the Sicilian mountain belt under the Tyrrhenian Sea. straints: (1) the deep-water marly carbonates of the Trubi unit
Furthermore, the extensional event produced the large fault testify that the studied fold and thrust belt was still largely
scarps hundreds of metres tall, some of which were changed submerged by the sea up to the lower Pliocene (3.6 Ma);
into sea cliffs, and allowed the deposition of the Marsala (2) the marine clastic deposits of the Agrigento fm. indicate
synthem along the drowned faulted-blocks that were affected that the emersion of the southern areas of western Sicily began
by subsidence during the Emilian-Sicilian regional stages. As after the post-Santernian (1.5 Ma ago); (3) the shallow-water
a result of a subsequent uplift event (during or shortly after the clastic deposits of the Marsala synthem and their relationships
Sicilian stage) these blocks gradually emerged starting during with the substratum show that the areas of the northern side
the Middle Pleistocene stage, as indicated by the present-day were above the surface in the pre-Emilian (before 1.5 Ma),
stair-step flights of uplifted marine terraces of the Middle- submerged during the Emilian–Sicilian interval (1.5 – 0.8 Ma
Upper Pleistocene stages, which are located in the northern ago), and again emerged from the Sicilian regional stage (after
coastal plains up to about 100-300 m a.s.l. Based on the alti- 0.8 Ma ago). Consequently, the emersion of the older areas of
tude of the inner edge of the MIS 5.5 and in agreement with central and northern Sicily and the beginning of the first relief
the researchers who studied these coastal areas (Mauz et al. modelling processes occurred between 3.6 –1.5 Ma ago.
1997; Antonioli et al. 1999, 2006; Di Maggio et al. 1999;
Scicchitano et al. 2011; Giunta et al. 2012; ; Sulli et al. 2013;
Basilone & Di Maggio 2016) the average rate of the post- Conclusion
Tyrrhenian uplift is between about 0.032 – 0.1 (NW coast) and
0.36 m/ky (NE coast). Generally, a few, large polycyclic The reconstruction of the geomorphological evolution of
coastal platforms overlooking the MIS 5.5 marine terrace western Sicily highlights the following:
developed where the uplift rate is less than 0.1 m/ky (e.g., • The occurrence of a very recent mountain belt, which
Trapani and San Vito lo Capo areas); while successions of several started its geomorphological evolution less than 3.6 Ma ago
orders of marine terraces consisting of smaller coastal plat- and only recently rose above sea level.
forms occurred where the uplift rate is higher than 0.1– 0.15 m/ky • The creation of new relief in the southern areas affected
(e.g., plain of Buonfornello; Sant’Agata di Militello area). by uplift, the causes of which are to be found in the elastic
On the northern side of Sicily, the post-Sicilian uplift causes rebound of the Iblean-Pelagian slab following the
of the previously subsiding blocks might be found in the con- south-westward constant migration of the accretionary
tinuous rise of the footwall of the extensional faults, which wedge and its foredeep.

GEOLOGICA CARPATHICA, 2017, 68, 1, 80 – 93