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content varying between 0.6-1%. The carbon isotope data for the aromatic and saturate fractions for the analysed bitumens point out a possible
correlation between these hydrocarbons and the oils generated by Late Triassic source rocks in the Ragusa Basin (Figure 7).

A comparison between the available geochemical data for the Ragusa Basin oils and the bitumens in western Sicily indicate the latter hydrocarbons
were generated in a more restricted marine environment characterised by carbonate sedimentation and absence of a clastic input. The gammacerane
index for the analysed bitumens is on average higher than in the Ragusa Basin oils, suggesting a well-developed stratification of the water column
and enhanced salinity. Diasteranes, which are indicative of presence of clays in the source rock, are absent in the analysed bitumens but present in
the Gela oil (Mattavelli et al., 1990). The C29/C30 hopane ratio is also higher in all the bitumens collected in western Sicily (ranging from 0.59 to
1.24), whereas it is less than 0.4 in the Gela and Ragusa oils (Mattavelli et al., 1990). The Ragusa Basin oils and the bitumens in western Sicily are
also characterised by a relative enrichment of %C29 regular sterane with respect to %C27 regular sterane, the ratio of the latter to the former being
in the range 0.45 to 0.66 in western Sicily, and 0.66 in the Gela oil (Mattavelli et al., 1990). This is likely indicative of a significant algal content in
the kerogen of these source rocks.

The Hydrocarbon Potential of Late Triassic-Liassic Source Rocks Offshore Western Sicily

The presence of seeps onshore western Sicily is limited to intraplatform basins within the Trapanese platform unit, no hydrocarbon seepage occurs
within the inner thrust belt in the Panormide platform unit (Figure 6). An example of intraplatform basin offshore Sicily is provided by organic rich
facies of Liassic age in the Nora Nord 1 well (re-examination of cores, JV internal report, R. Di Cuia, 2010). The oil from the Narciso-1 discovery has
been tied to a carbonate source rock which is likely the same for the analysed bitumens and the Marineo Basin. Oil shows in Nada-1 were also likely
generated from a carbonate source rock as suggested by the low API gravity, the high sulphur and the low paraffinic contents of this oil.
The hydrocarbon potential of Late Triassic-Liassic source rocks in the offshore thrust belt is unknown as no stratigraphic information is available in
the area (only one well, Emione-1, has been drilled). The Marettimo Island (Figure 2, Figure 5) displays sequences which could be representative of
part of the stratigraphy expected in the study area in the offshore thrust belt. There is no evidence of intraplatform basins of Liassic age in this
island, however organic rich facies are represented by dolomitic sequences of the Sciacca Formation (Late Triassic) deposited in a lagoonal to sabka
type environment, the potential of which is still unknown.

The Cretaceous Petroleum System

Tectonic Setting of Late Cretaceous Source Rocks Onshore Sicily

Cenomanian-Turonian organic rich facies were sampled in north-eastern Sicily in proximity of the villages of Floresta and Novara di Sicilia (Figure
3 and Figure 5). These sequences are considered as part of the Argille Scagliose Formation, described by Cavazza et al., 1997, as a melange unit
characterised by a fine grained matrix bearing huge exotic blocks which include nummulitic calcarenites, quartz-arenitic turbidites of the Numidian Flysch,