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ARTICLE IN PRESS 251
C. Lo Iacono, J. Guille´n / Continental Shelf Research 28 (2008) 245–256
Fig. 6. Distribution of subaqueous dunes around the Marettimo inner The largest dunes in the area were observed along the
western sector of the Marettimo shelf at a depth range of
shelf. Bathymetric contours every 10 m. a: subaqueous dunes with 20–35 m and for an average lateral extension of almost
1olo1.5; b: subaqueous dunes with 1.5olo2 m; c: subaqueous dunes 700 m (Fig. 7). The dune crests display a NNE–SSW
with 2olo2.5 m. Line orientation indicates main dune direction. orientation, forming a low angle with the coastline. The
maximum wavelength value observed on these dunes was
2.5 m. At the margins of the dune field the crest lines
become sinuous and bifurcated. Their median grain size
ranges from 5.6 to 8 mm, with the presence of frequent
pebbles and cobbles.
Sorted bedforms were only observed in the northeastern
sector of the Marettimo shelf on a particularly steep shelf
portion (2.51 gradient) (Figs. 4 and 8). They correspond to
a high contrasted acoustic facies in SSS records constituted
by light high backscatter bands alternating with darker low
backscatter areas. These bedforms are developed in a W–E
direction, almost perpendicular to the coast, from a depth
of about 35 m to the depth limit of this survey—
approximately 50 m. The sorted bedforms show a width
ranging from 15 to 50 m and a longitudinal extension
ranging from 50 to almost 300 m. They display linear
bands, changing to bifurcations and irregular patchy
shapes in the deepest part of the area (50–60 m). Bottom
sediment samples reveal that the dark acoustic bodies
correspond to medium sands (D50=0.2–0.3 mm), while
dive observations along the lighter backscatter bands
reveal strongly bioturbate, poorly sorted sandy gravel
Fig. 7. SSS image showing (a) gravelly subaqueous dunes of the western Marettimo inner shelf (approximate depth: 35 m; approximate l: 2.5 m).
(b) Linear pattern and flat crest. (c) Grain size of dune sediments, dominated by gravels and pebbles.
