Page 2 - Sulli_ali_2011

15/3/2018 SEDIMENTARY DYNAMICS OF THE MARETTIMO CONTINENTAL SHELF AND MARETTIMO CHANNEL (EGADI ISLANDS – WESTERN MEDITERRANEAN): ANALYSIS OF DEPOSITIONAL AND E…
Different morphologic features were recognized through side scan sonar, multibeam and high-resolution = OA Link
seismics, acquired in the framework of national Research Projects (CARG, GebecSud, MaGIC) carried out by the
Department of Earth and Marine Science (former Department of Geology and Geodesy) of the University of
Palermo. Sediment samples have been also collected and analyzed. The Egadi Islands are part of the NW Sicilian
offshore, and belong to the mountain chain that connects the Sicilian chain to the Maghrebides one. The
Marettimo Island represents an isolated portion of the Egadi continental shelf and is separated from the rest of
the archipelago by the Marettimo Channel. Previous studies allowed to recognize different kind of sedimentary
structures along the seafloor. Lo Iacono and Guillén (2008) described extensive field of subaqueous dunes
(Ashley, 1990) along the Marettimo inner shelf, forming on gravelly and pebbly sediments and related to strong
storm events (H:5.5 m, T: 12 s). Larger dunes have been observed in the north-western sector of the inner shelf
with wavelengths ranging from 1 to 2.5 m, heights between 15 cm and 30 cm and extending laterally for
hundreds of meters. Moreover in the north-eastern sector of the inner shelf, sorted bedforms have been detected
at a depth of 40 m: they are characterized by a width varying between 15 m and 50 m and a length that reaches
hundreds of meters. In the south-eastern sector of the Marettimo outer shelf, Colantoni et al. (1993) map two
groups of sedimentary structures. In the same area, Lo Iacono (2004) recognized two-dimensional and three-
dimensional subaqueous dunes. 2D dunes are found at depths between 60 and 90 m and show a wavelength
variable between 15 and 50 m. 3D dunes, which are found at a depth of 80 m, are characterized by a wavelength
of 30 m and a lateral extent of 50 m. Morphological evidences of a strong hydrodynamic regime come also from
the morphobathymetric analysis of the Marettimo Channel, that is a 24 km long submarine valley oriented
NNW-SSE, with a depth ranging from a minimum of 180 m to a maximum of 370 m and a width from 2 km to
14 km. Inside the channel, south of its narrowest point, a 180 m deep bathymetric threshold separates two areas,
which deepens towards opposite directions: north-west and south. The flanks of the sector that deepens towards
the NW are affected by mass-wasting features (Lo Iacono et al., 2007). The western flank of the channel, which
delimits the Marettimo continental shelf, is carved by gullies, making the shelf-edge very uneven. Gullies develop
to a maximum depth of 280 m and have a length of 250 m and a width of 50 m. At the bottom of the channel a
linear incision 20 m deep, 400 m wide and almost 3 km long, is probably generated by erosive bottom currents.
On the whole, the morpho-sedimentary structures here described reveal a strong hydrodynamic regime. The
morphological and textural features of the bedforms observed on the Marettimo inner continental shelf suggest
the occurrence of sporadic medium to strong storm events coming from western sectors. The morphological
characteristics of the Marettimo Channel reveal the occurrence of strong bottom currents probably related to the
severe interchange of water masses between the Tyrrhenian Sea and the Sicily Channel. References: Ashley, G.,
1990. Journal of Sedim. Petrology 60, 160–172. Colantoni, P., Ligi, M., Morsiani, M.P., Penitenti, D., 1993.
UNESCO Reports in Mar. Science 58, 93–98. Lo Iacono, C., 2004. Università di Napoli ‘‘Federico II,’

https://pure.unipa.it/it/publications/sedimentary-dynamics-of-the-marettimo-continental-shelf-and-maret-2 2/3