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Late Quaternary sedimentary complexes along the Marettimo Valley
(Egadi Islands, western Sicily offshore)

M. AGATE (*), M. SPROVIERI (**), S. PASSARO (°), S. TAMBURRINO (**)(°), A. SULLI (*), M. VALLEFUOCO (°), L. GIARAMITA (**), F.
PLACENTI (**), S. POLIZZI (*), C. LO IACONO (°°), A. INCARBONA (*) & F. BUTERA (*)

(*) DIPARTIMENTO DI SCIENZE DELLA TERRA E DEL MARE – UNIVERSITÀ DI PALERMO, ITALIA
(**) ISTITUTO PER L’AMBIENTE MARINO COSTIERO IAMC-CNR, CAMPOBELLO DI MAZARA (TP), ITALIA
(°) ISTITUTO PER L’AMBIENTE MARINO COSTIERO IAMC-CNR, NAPOLI, ITALIA
(°°) NATIONAL OCEANOGRAPHY CENTRE, SOUTHAMPTON, UNITED KINGDOM

Keywords: Contourite drifts, Egadi Island, Late Quaternary, Prograding depositional systems.

Across the Egadi Island archipelago (western Sicily offshore), the Marettimo Valley is located at shallow to
intermediate water depths (150 - 450 m) and it is crossed by bottom current probably related to Levantine
Intermediate Water that clockwise flows around Sicily island. The Valley is about 30 km long, has a minimum
width of 1.8 km between the continental shelf edges of Marettimo island and Favignana island, and displays
both depositional and erosional settings. Erosional settings are mostly centered in the central sector of the
Valley where lower Quaternary as well as pre-Quaternary rocks outcrop on the sea floor.
On the peripheral sectors of the Valley, late Quaternary progradational complexes accumulated along both
eastern and western flanks. South-west of the Favignana island, these progradational complexes,
investigated by means of high resolution seismic profiles and also mapped using multibeam morpho-
batymetric data, consists of two types of seismic facies units: - unit A displays reflection-free seismic facies
and thin, low- amplitude, inclined reflectors with downlap terminations onto the lower boundary, and
erosional truncation at the upper boundary; these seismic facies are referable to oblique-tangential
clinoforms displaying variable height and wedge-shaped external geometry; -unit B shows continuous,
parallel, slightly concave reflectors and, towards the central sector of the Valley, continuous, sub-horizontal
reflectors that form a deposit having a very broad low-mounded geometry; lateral transition in between
concave and sub-horizontal reflectors is characterized by channelized erosional truncations; landwards, this
unit wedge-out with onlap lateral termination on the offsets of the clinoformed wedges. Top wards, these
latter are topped by an erosional transgressive surface formed during the last eustatic sea-level rise, locally
covered by Holocene deposits.
The prograding sedimentary complex detected along the south-western Favignana offshore continuously
extend for about 15 km; smaller progradational complexes have been recognized also in the norther sector
of the valley and, scattered, along the western flank (Marettimo Island continental shelf margin).
According to our seismo-stratigraphic analysis, the two very different seismic facies units represent two
distinct sedimentary deposits: - unit A accumulated by progradation of shallow-water deposits during
eustatic forced-regression; unit B is referable to contourite drifts deposited by bottom currents through the
Marettimo Valley.
Mutual interaction can be envisaged between progradational growth of the margin and contourite
accumulation: progradation progressively reduces the width of the Marettimo valley producing acceleration
of bottom current inside; contourite deposition creates a landward gradient of the depositional ramp forcing
a decrease of the clinoforms height and, with constant sedimentary supply, an increase of the progradation
rate.

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