Page 59 - MSc_thesis_R A Kil

During the Lower Pleistocene, the Mediterranean area faces a relatively high sea level (Cohen & Gibbard,
2010). The chronostratigraphical correlation presented in figure A.5 (appendix A) presents the sea level
curve — represented by marine isotope analysis — from the Lower Pleistocene to present. The uplift phase
ongoing since the stage ended in the Plio-Pleistocene period (Tavarnelli et al., 2003) is causing the existing
structures of Favignana, Levanzo and Marettimo to experience an inversion process. As a consequence of
the uplift carbonate producing platforms started to become prone to erosion by storm-induced currents
and wave action.

Because of the position of Monte Santa Caterina with respect to the early mountains of Marettimo
and in particular Levanzo, a negative structure — such as a channel — existed. The high thickness of
the Plio-Pleistocene between Favignana and Levanzo reported by Abate et al. (1997) suggests that this
hypothesis is likely. Large amounts of bioclastic material were delivered to the area, and deposited on top
of the Trubi clay. Similar Mediterranean calcarenites described by D’Angelo et al. (2005) and Hansen
(1999) are interpreted as being deposited on the shelf, and then reworked by storms which induces the
build up of bioclastic wedge that builds out towards the open sea. More discussion on similar deposits
is provided later. The two main transport directions on Favignana indicate progradation towards the
mainland of Sicily.

Based on the observations mentioned above, the development of the Favignana calcarenite, the resulting
stratigraphy and the overall geological model can be reconstructed in the following three phases:

1. The deposits that characterise the base of the Favignana calcarenite sequence generally have a rather
massive character. Vast amounts of sediments were transported and deposited at a very high rate on
top of the Zanclean Trubi clay. As water depth decreases, due to 1) the accumulation of bioclastic
material on the seafloor; 2) uplift of the area like observed in the Marsala calcarenite by D’Angelo
et al. (2005); or 3) sea level drop that steadily occurred during the Lower Pleistocene, lamination
starts to develop. The lower plane parallel laminated sands are in some cases relatively extensive.
As the accommodation space starts to decrease more, small scale dunes with either undulated or
straight crest start to develop. Because of the directions of the storm-driven current and wave
action, propagation is mainly to the south-southeast. Minor storms from the south reversed the
process from time to time. A high degree of fluctuations in depositional energy is observed in the
field, which is illustrated by erosive features and the varying thickness of smaller dune foreset beds.

2. Due to the processes described in phase one, accommodation space continued to decrease, resulting
in a further increase in energy under which the Favignana calcarenite is deposited. Locally 15
metre high giant dunes are observed in large parts of the fieldwork area, which can be relatively
laterally continuous. More storms induced incidental supercritical flow conditions, providing energy
to develop undulated bedding. During this stage, a substantial complex with submarine prograding
calcarenite dunes is generated.

3. A high positive structure — like the crest of a giant bioclastic calcarenite dune — is in case of

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