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192 F. Pepe et al. / Geomorphology 303 (2018) 191–209
for the coast of southern central Turkey; Morhange et al. (2006) for the Three faults systems offset both the Mesozoic-Cenozoic and the
Tripoli islands and Byblos, northern Lebanon; and Scheffers and Lower Pleistocene deposits (Fig. 1A). The first system, which are N-S
Scheffers (2007) for the coastline Crete (Greece). strike-slip faults, bounds the ridge of Favignana and it reactives/dis-
The availability of blocks detached from emerged and submerged places the Miocene thrusts somewhere (Nigro and Renda, 2000;
platform edges is essential to provide material which can be subse- Renda et al., 2000; Gueguen et al., 2002; Giunta et al., 2009). The other
quently transported and deposited along the coastal zone. The size faults systems are high-angle strike-slip structures oriented approxi-
and shape of the boulders are frequently determined by litho- mately either W-NW (right-lateral) or N-NE (left-lateral).
structural features of rocky platform (e.g. Whelan and Kelletat, 2005; The Lower Pleistocene grainstones are affected by three main sets of
Kogure et al., 2006; Hansom et al., 2008; Knight and Burningham, deformation bands. One of these sets occurs parallel to bedding, while
2011; McKenna et al., 2011). Among these, bedding planes and high- the others sets are mutually cross-cutting and form a pair of conjugate
angle to bedding fracture networks are considered planes of weakness strike-slip faults oriented N-S- and NW-SE. The bedding-parallel set
in which weathering and waves act to break up the platform was interpreted to contain compaction bands (Tondi et al., 2012).
(Stephenson and Naylor, 2011, and references therein). Despite a
large number of studies that rely on reconstructing event histories by 2.2. Geomorphological setting
assessing boulder size, distance travelled, elevation attained and esti-
mating the wave energies required to deposit large boulders, little re- Favignana is the largest island of the Aegadian Archipelago. Its mor-
search has considered issues of the geological controls on boulder phological setting is characterized by two uplifted and gently seaward
production in a rock coast setting along the coast of the central Mediter- sloping (5°–10°) shore platforms shaping Lower Pleistocene deposits.
ranean Sea. The abrasion surfaces extend over the Punta Faraglione and Punta
Starting from a deterministic approach, the scientific community Fanfalo coastal areas located, respectively, in the NW and SE sectors of
recognizes that numerical hydrodynamic analysis is an important tool Favignana Island, and separated by a ~300 m high carbonate ridge,
for estimating the wave height and energy that satisfy the requirements trending roughly N-S (Fig. 1A). The carbonate slopes dip seaward as
for initiating the transport of a boulder, considering its pre-transport sub-vertical cliffs in the northeastern sector of the ridge. Debris flow de-
setting and type of movement (e.g. Nott, 1997, 2003; Noormets et al., posits formed along the transition area between the carbonate ridge and
2004; Pignatelli et al., 2009; Benner et al., 2010; Nandasena et al., the abrasion surfaces.
2011; Engel and May, 2012). These models have been used to try to de- Along the western sector of Favignana Island, the coastline is indent-
termine whether tsunamis or storm waves are responsible for boulder ed due to presence of faults and erosion processes along the weakened
emplacement. joint planes of the rocks. The common features in the littoral geomor-
The aims of this study are: a) to improve knowledge on the control phology of this sector are the carbonate cliffs. On the contrary, the east-
exerted by the thickness of bedding planes and spacing of bed- ern coastal zone is marked by alternation of high cliffs (~40 m) and
perpendicular fractures of rock coast over the number, initial size and sandy beaches that gently slopes towards the sea.
shape of boulder-sized source material that may be detached from the From a biological point of view, almost the entire coastal area is char-
rockhead; b) to determine the process responsible for the transport acterized by vermetid trottoirs up to several centimeters thick, which
and accumulation of boulders in two sites of the Favignana Island extend to the nearshore up to 10 m below sea level. Trottoirs consist
(offshore of north-western Sicily) coast; and c) to present a qualitative of intertidal reef constructions of gastropod molluscs (Vermetus
and quantitative methodological method to establish the relationships triquetrus sp. and Dendropoma petraeum sp.) in association with red
between sediment source and bolder deposits observed along many algae (Antonioli et al., 1999; Balistreri et al., 2015).
coastal areas. We analyze a dataset of boulders and rupture surfaces,
which are termed sockets by Knight and Burningham (2011) and corre- 2.3. Oceanographic setting
spond to holes due to the boulder detachment from the rockhead.
The Aegadian Archipelago is located in a sector of the Central Medi-
2. Study area terranean Sea affected by major marine weather perturbations. Liberti
et al. (2013) and Besio et al. (2016) have analyzed the wave energy of
2.1. Geological setting the Mediterranean Sea by using a third generation ocean wave model,
respectively, for the period 2001–2010 and 1979–2015. Results indicate
Northwestern Sicily and its western offshore prolongation (Box 1 in that the average wave energy in the Aegadian Archipelago follows a pat-
Fig. 1A) is a segment of the early Miocene to Recent Sicilian-Maghrebian tern where the most energetic waves occur during the winter while the
Fold and Thrust Belt (SMFTB). The latter consists of a thin-skinned, lowest wave energy occurs during the summer season. The seasonal av-
south-verging fold and thrust system formed by Mesozoic–Cenozoic erage power per unit crest has been computed to be 14–15 kW/m,
carbonates, siliciclastic and evaporites deposits, locally overlain by late 10–11 kW/m and 3–4 kW/m, respectively, during the winter, spring
orogenic clastic deposits (Catalano et al., 2000; Sulli, 2000). The Egadi and fall and summer seasons. These values indicate that the Aegadian
Archipelago is a segment of the westernmost sector of the SMFTB Archipelago lies in one of the most energetic area of the Mediterranean
(Abate et al., 1997, 1999; Nigro and Renda, 2001). Sea.
Favignana Island, which belongs to the Aegadian Archipelago, is built
up of Mesozoic-Lower Cenozoic carbonate deposits unconformably cov- 3. Materials and methods
ered by bluish marls and shale of the Middle-Late Pliocene followed by
yellowish grainstones of the Early Pleistocene and by calcarenites and This study is based on the integration of various datasets obtained
biorudites of the Late Pleistocene (Tyrrhenian) (Catalano et al., 1996; from field surveys, laboratory analysis of rock bulk density, 14 C AMS dat-
Incandela, 1996; Abate et al., 1997). The Lower Pleistocene deposits ing, isobaths digitized from a nautical chart, numerical hydrodynamic
are widespread along the whole eastern half of the emerged paleo- analysis, and hindcast numerical model of wave characterization.
Favignana Island in a pull-apart basin as well as in the northwestern sec-
tor (Fig. 1A). The yellowish grainstones are mainly composed of 3.1. Field survey
bioclasts (i.e. Vermetus, Serpula, bivalves, echinoids, algae and corals).
Calcite cements are present in small amounts and consist of microsparry Fieldwork was carried out in August 2015 to identify boulder de-
cement at grain contacts and/or within intra-granular pores as well as posits and sockets along two coastal areas of Favignana Island. Among
syntaxial overgrowth cement encompassing echinoid plates and spines. N200 boulders and 90 sockets detected, the most representative in