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POSTER

SPATIAL AND TEMPORAL VARIABILITY IN THE SHALLOW-MARINE
FAVIGNANA CALCARENITE (SICILY, ITALY)

Arnoud Slootman1*, Andrea Moscariello1

1Earth and Environmental Sciences, University of Geneva, 13 rue des Maraichers, 1205 Geneva, Switzerland
*corresponding author: Arnoud.Slootman@unige.ch

Favignana (18 km2) is the principal island of the Egadi Archipelago located offshore from western Sicily in the
central western Mediterranean. The geology of the island’s eastern part consists of Lower Pleistocene, coarse grained
calcarenites, composed mostly of a Heterozoan assemblage (e.g. red algae, bivalves, echinoids, bryozoans, benthic
foraminifera) which is interpreted as the result of production and redeposition of skeletal debris in a coastal to shallow-
marine system.

In Early Pleistocene times, the paleo-islands of Favignana and Levanzo were located on the outer shelf of the Sicilian
western offshore, separated from Sicily by a 10 to 15 km-wide, N-S striking sea strait, in which deposition of the
calcarenites took place. Based on palaeoflow analyses, the carbonate factory which produced the skeletal sand and
gravel is inferred to have been located in a sub-marine sill between the two islands.

Upper shoreface deposits onlap the eastern side of the Favignana mountain ridge. During persistent (storm) winds,
material was shed into deeper settings below wave base, giving rise to the formation of a ramp-slope descending ca.
50 metres into shelfal depths. Facies are dominated by decimetre to metre-scale dune cross-stratification dipping
towards a prevailing southeastern direction, corresponding to ramp-slope progradation. On the flat offshore of the
shelf, wind-driven currents through the strait generated cross-strata dipping either north or southward. Interaction
with the ramp-slope toesets is apparent from the abrupt termination of dune beds against the prograding ramp. Cross-
stratified deposits show intense Thallasinoides bioturbation.

The succession is interrupted by up to 10 metres-thick beds, characterised by supercritical flow and dewatering
structures, erosive bases, the absence of Thallasinoides bioturbation, and the presence of rare Ophiomorpha escape
burrows. Such beds were interpreted as catastrophic event beds, possibly linked to infrequent megastorms or tsunamis
generated by active tectonic structures. The alternation of dune and event beds imposes a strong bimodal character
on the deposits.

Here, we present some descriptions of key outcrops illustrating the spatial and temporal variability of this dynamic
clastic carbonate system. Compared to siliciclastic environments, clastic carbonates achieved relatively little attention,
despite a significant presence throughout the Mediterranean basin. We emphasise the catastrophic nature of the
studied shallow-marine calcarenite, ca. 50% of which was deposited during short-lived, high-energy events.

48 British Sedimentological Research Group AGM, Nottingham 2014