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Geomorphology 303 (2018) 191–209

Contents lists available at ScienceDirect
Geomorphology

journal homepage: www.elsevier.com/locate/geomorph

Boulder coastal deposits at Favignana Island rocky coast (Sicily, Italy):
Litho-structural and hydrodynamic control

a
a,
a
c
b
Fabrizio Pepe ⁎, Marta Corradino ,NicolòParrino , Giovanni Besio , Valeria Lo Presti ,PietroRenda a,d ,
e
e
Lucio Calcagnile , Gianluca Quarta , Attilio Sulli a,d , Fabrizio Antonioli c
a
Dipartimento di Scienze della Terra e del Mare, Via Archiraﬁ 22, Università di Palermo, Italy
b
Dipartimento di Ingegneria Civile, Chimica e Ambientale, Università degli Studi di Genova, Via Montallegro, 1, 16145 Genova, Italy
c
ENEA Agenzia Nazionale per le nuove tecnologie, l'energia e lo sviluppo sostenibile, Via Anguillarese 301, S. Maria di Galeria, Rome, Italy
d Istituto Nazionale di Geoﬁsica e Vulcanologia, sez. di Palermo, Via Ugo la Malfa 153, Palermo, Italy
e
CEntro di DAtazione e Diagnostica (CEDAD), Dipartimento di Matematica e Fisica “Ennio De Giorgi”, Università del Salento, Via per Monteroni, Lecce, Italy
article i nfo abstract
Article history: Boulders are frequently dislodged from rock platforms, transported and deposited along coastal zones by high-
Received 14 July 2017 magnitude storm waves or tsunamis. Their size and shape are often controlled by the thickness of bedding planes
Received in revised form 15 November 2017 as well as by high-angle to bedding fracture network. We investigate these processes along two coastal areas of
Accepted 19 November 2017 Favignana Island by integrating geological data for 81 boulders, 49 rupture surfaces (called sockets) and fracture
Available online xxxx
orientation and spacing with four radiocarbon dates, numerical hydrodynamic analysis, and hindcast numerical
simulation data. Boulders are scattered along the carbonate platform as isolated blocks or in small groups, which
Keywords:
form, as a whole, a discontinuous berm. Underwater surveys also highlight free boulders with sharp edges and
Boulders
Fracture network sockets carved out in the rock platform. Boulders are composed of ruditic- to arenitic-size clastic carbonates.
Hydrodynamic equations Their size ranges from 0.6 to 3.7 m, 0.55 to 2.4 m, and 0.2 to 1 m on the major (A), medium (B), and minor
Storm waves (C) axes, respectively. The highest value of mass estimation is 12.5 t. Almost all of boulders and sockets are char-
acterized by a tabular or bladed shape. The comparisons between a) the fractures spacing and the length of A- and
B-axes, and b) the frequency peaks of C-axis with the recurrent thickness of beds measured along the coastal zone
demonstrate the litho-structural control in the size and shape of joint-bounded boulders. These comparisons, to-
gether with the similarity between the shapes of the boulders and those of the sockets as well as between the
lithology of boulders and the areas surrounding the sockets, suggest that blocks originate by detachment from
the platform edge. Thus, the most common pre-transport setting is the joint-bounded scenario. Hydrodynamic
equations estimate that the storm wave heights necessary to initiate the transport of blocks diverge from ~2 m
to ~8 m for joint-bounded boulders and from few tens of centimeters up to ~11 m for submerged boulders.
The comparison between the wave heights at the breaking point of the coastal zones with the results of hydro-
dynamic equations shows that waves approaching the coastline are able to transport all surveyed boulders. Our
data suggest that boulders have been transported by several storm events, even in very recent times.
© 2017 Elsevier B.V. All rights reserved.

1. Introduction the coastal area (e.g. Mastronuzzi and Sansò, 2004; Hall et al., 2006;
Hansom et al., 2008; Suanez et al., 2009). Examples of boulders
Coastal boulder deposits, organized into distinctive ridges, berms, transported and deposited along the central Mediterranean Sea coasts
and mounds, are frequently observed either along rock platforms as a consequence of high-magnitude storm waves or tsunamis are doc-
edges or on top of bedrock cliffs at different heights (e.g. Trenhaile, umented by Mastronuzzi and Sansò (2004, 2000) and Mastronuzzi et al.
2005; Scicchitano et al., 2007; Goto et al., 2009; Etienne and Paris, (2007) for the Ionian Coast (Italy); Mastronuzzi and Pignatelli (2012)
2010; Furlani et al., 2014). Boulders were often described as blocks de- for the Ionian coast of Apulia; Barbano et al. (2010) and Scicchitano
tached from platform edges, and then transported and deposited along et al. (2007) for the Ionian coast of south-eastern Sicily (Italy); Biolchi
et al. (2016) for the coast of Malta; Shah-Hosseini et al. (2016) for the
Mediterranean coast of Egypt; Shah-Hosseini et al. (2013), Vella et al.
⁎ Corresponding author at: Dipartimento di Scienze della Terra e del Mare, Via Archiraﬁ,
22, 90123 Palermo, Italy. (2011) and Piscitelli et al. (2017) for the Southern France; and Nappi
E-mail address: fabrizio.pepe@unipa.it (F. Pepe). et al. (2017) for the Salento Peninsula (Italy); Öğretmen et al. (2015)

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