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A possible Tertiary source rock for the Gagliano oil was also identified on the basis of small amounts of oleanane (oleanane index of 0.04, L.
Mattavelli et al., 1990). However the reliability of this biomarker appears questionable as small traces of oleanane could have been picked up by oil
migrating through Late Cretaceous and Tertiary rocks (L. Mattavelli, 1990). Oleanane was not found in any of the hydrocarbons seeps analysed in
Sicily.

Other Potential Source Rocks in Sicily

Organic rich pebbles in the Argille Scagliose Formation (Early Tertiary, Sicilide Unit) were collected in central Sicily, close to the village Villarosa.
These samples showed excellent hydrocarbon generating potential with TOC concentrations up to 46%, HI up to 515 and excellent petroleum
potential of up to 238.7 kg HC/ton. However organic rich pebbles are dispersed into a clay matrix and are generally quite rare in the outcrops.
Another issue of these sequences is the lack of sufficient burial to generate hydrocarbons which could only be attained in the most internal domains
of the thrust belt.

Expected Stratigraphy and Basin Modeling Study in the Offshore Thrust Belt

A stratigraphic model for the offshore thrust belt has been built based on correlations between northern Tunisia and Sicily. Following possible
analogies with the onshore Sicilian thrust belt, the model considers the occurrence of allochthnous pelagic units (Late Triassic-Early Tertiary) with
interbedded resedimented carbonates overlying a repeated thick carbonate succession (Late Triassic-Early Tertiary) which has similar characteristics
to the onshore Panormide platform. A review of the available data on the Prepanormide succession in Marettimo Island (Figure 5) indicates the
presence of turbidites and resedimented carbonates (Early to Late Jurassic) which could have been sourced from an equivalent Panormide platform.
Resedimented carbonate intervals which formed in a similar paleotectonic setting onshore Sicily have been correlated with sea level fall and shelf
margin collapse (Panormide-Imerese correlation, L. Basilone, 2008). The Panormide platform is the only domain in this region which is
characterised by an unconformity with subaerial exposure (presence of bauxites, L. Basilone, 2008) which locally extends from the Early to the Late
Jurassic. The presence of shallow water carbonate sedimentation throughout the Cretaceous is another peculiarity of the Panormide platform. As
previously pointed out, geochemical data indicate Late Cretaceous source rocks, which likely generated oil within the offshore thrust belt, are
characterized by a near-shore environment of deposition.

Source rock maturity modeling has been undertaken in the inverted Messinian Tortonian foredeep using the 1D Petromod software. The results
obtained have been extrapolated to the offshore thrust belt where different hypothetical tectono-stratigraphical models have been considered.
A basal heat flow of 60 mWm2 has been used in the modelling, this value has been derived from published maps and reservoir temperatures from
corrected bottom hole temperatures. Calculated maturities have been compared to actual maturities derived from vitrinite data in the available wells
(Figure 8), and a reasonable match has been achieved. A linear function of depth versus maturity has been determined for the top Triassic showing
the top of the oil window occurring at approximately 2.5 Km (Figure 9). Fluid flow studies onshore Sicily have shown hydrocarbon migration
occurred in the Middle-Late Miocene, coinciding with the maximum burial reached in the thrust belt, (B. Dewever et al., 2010). Assuming limited