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F. Pepe et al. / Geomorphology 303 (2018) 191–209 201
Table 1
Location, Dunham and Folk classes, granulometric-compositional classification, mass, volume and bulk density of the 10 rock samples extracted from boulders detected along Punta
Faraglione and Punta Fanfalo coastal areas. Boulder's thickness indicates the C-axis. The bulk density was calculated as the ratio of mass to volume. Mass was measured by using a precision
balance with a scale's readability of 0.1 g, whereas the volume was estimated following the “Instantaneous Water Immersion Method”.
Sample Sample Dunham classes Folk Granulometric-compositional Boulder's thickness Mass Volume Bulk density
3
3
ID location classes classification (cm) (g) (ml = cm ) (g/cm )
1 Punta Faraglione Grainstone-packestone Fossiliferous polygenic-conglomerates 30 711.2 300 2.37 ± 0,08
3 Punta Faraglione Grainstone Biomicrite Bioclastic fine-calcarenites 50 781.2 350 2.23 ± 0,06
5 Punta Faraglione Wakestone - packestone Fossiliferous polygenic-conglomerates 70 338.8 150 2.25 ± 0,17
7 Punta Faraglione Grainstone Bioclastic coarse-calcarenites 40 315.2 150 2.10 ± 0,14
8 Punta Faraglione Grainstone-packestone Biomicrite Bioclastic coarse-calcarenites 70 420.9 225 1.87 ± 0,08
9 Punta Fanfalo Grainstone-packestone Biomicrite Bioclastic fine-calcarenites 30 424.6 220 1.93 ± 0,09
10 Punta Fanfalo Grainstone Biomicrite Bioclastic fine-calcarenites 70 381.3 200 1.90 ± 0,09

detached from the shore platform. Moreover, the comparison between coastline in the Punta Fanfalo coastal area. Although its orientation
the fracture spacing of the Far1 and Far 2 sets with the B- and A-axes di- with respect to the coastline is not sufficient for geological-structural
mensions of boulders accumulated along the Punta Faraglione coastal analysis, it is of fundamental importance to the formation of predicted
zone suggests that a close relationship exists between the class width boulders. In fact, by considering that only one fracture set cannot create
of fracture spacing and the B- and A-axes of the boulders (Fig. 9c, d). joint-defined blocks we speculate that the reduced number of boulders
Only the class width 2–2.3 m of the Far 1 fracture spacing shows no cor- deposited in this area is can be related to the lack of high-angle fracture
respondence with the B-axis of the measured boulders. This may indi- sets developed orthogonally between them. Based on our data, we con-
cate that their formation could be related to different fractures spacing clude that the spacing and orientation of high-angle fracture sets to-
probably formed in layers different from the one analyzed, or by the gether with the thickness of bedding planes are key parameters in
Far 3 fracture set that is poorly documented by our dataset. determining the initial shape and size (A, B, C-axes) of joint-defined
Several boulders also display sharp edges characterized by straight boulders in the rocky coast setting.
surfaces forming angles in the range between 60° and 90° (Fig. 2n).
These values are quite similar to those measured between the Far1 5.2. Comparison between hydrodynamic equations results and the hindcast
and Far 2 and/or Far3 fracture sets (Fig. 9b), thereby demonstrating data
that the high-angle to bedding fracture strongly influence the shape of
boulders. In order to understand if the waves approaching the coastline were
The amount of boulders deposited along the Punta Faraglione coast- able to transport the boulders, the wave height H S (Table A3), necessary
al area is considerably higher than that found in the Punta Fanfalo coast- to initiate the transport of each boulder, is compared with the wave
al area. Considering that both localities expose part of the same height at breaking point for the coastal zones H b (Table A4). By assum-
prograding beach/near foreshore complex system, and hindcast data re- ing that the direction of the A-axis and of the wave responsible for the
lated to the Favignana offshore (Besio et al., 2016) does not show signif- transport of boulder are approximately parallel, the values of H S and
icant differences in the waves height, we infer that the difference in the H b , can be compared only when they are related to the waves that prop-
amount of boulders could be linked to the geological properties of the agate in the same direction. Therefore, five offshore wave direction
rock-source material responsible for the formation of the boulders. ranges were selected, following the method described in Section 3.7,
Fig. 9b highlights that Fan 1 has formed at low-angle (~35°) to the and the maximum values of H b were chosen for every range. Also, the

Fig. 9. a) Plan view of the fracture sets Far 1, Far 2 and Far 3 detected on the Punta Faraglione coastal area; b) rose diagrams of orientations of fracture sets. The dashed line indicates the
average direction of the coastline. Note that the Far 1 set is almost parallel, while Far 2 and Far 3 are almost perpendicular to the NE-SW-trending coastline of Punta Faraglione. The Fan 1 set
forms an angle of ~35° to the NNW-SSE-trending coastline of Punta Fanfalo; c and d) histograms of the distribution, respectively, of the Far 1 spacing and the B-axes, and the Far 2 spacing
and the A-axis of boulders measured in the Punta Faraglione coastal areas.