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Cenomanian-Turonian organic rich facies and roughly coeval fossiliferous marly limestone known as “Cenomaniano in Facies Africana” (Vincenzi
et al., 1997, G. Scopelliti et al., 2008). The latter sequences have been correlated with equivalent lithofacies outcropping in Tunisia, the Zeggab
Formation which formed within the shallowest portions of a carbonate ramp system, whereas the organic rich shales were deposited in deeper water
on the distal ramp (G. Scopelliti et al. 2008).

The Argille Scagliose Formation has been considered by some authors to be the result of gravity flows dismantling a depositional carbonate ramp
located southward and subsequently involved in a tectonically active front inside an accretionary wedge (G.Scopelliti et al., 2008). A southern
provenance, probably not far from the region which is now Tunisia, was proposed for the Novara di Sicilia exotic blocks (G. Scopelliti et al., 2008).
However the “exotic” organic rich friable shale blocks appear undeformed, implying that they could not have travelled a large distance in a gravity
driven flow and that they were likely to be tectonically displaced during the collision of the African units with the European Kabylie basement. It is
suggested that these sequences formed within slope facies of the Panormide Platform domain and were emplaced on the Argille Scagliose Formation
by large back thrusts during the Langhian tectonic event.

Geochemistry and Implications for Petroleum Exploration in the Offshore Thrust Belt

The Cenomanian-Turonian black shales outcropping in northeastern Sicily, regarded as a unit equivalent to the Bahloul Formation in North Africa,
have the highest source rock potential of all the analysed samples. This is indicated by the high TOC ranging from 3% in the most carbonate rich
intervals to 29.8% in the shaly levels. Measured Hydrogen Index varies from 412 to 649 indicating type I/II organic matter, with excellent petroleum
potential of up to 183.33 kg HC/ton. The geochemical data presented in this study are in good agreement with previous analyses carried on the same
outcrops by the University of Palermo (G. Scopelliti, 2008). The thickness of the exposed Cenomanian-Turonian organic rich interval in Novara di
Sicilia is in the order of 19 m, however correlations based on organic and carbonate carbon isotope suggest that only phase A of the Cenomanian-
Turonian anoxic event is represented in this location (G. Scopelliti et al., 2008). The moderate diasterane content and the low tricyclic C22/C21 and
C24/C23 ratios are indicative of a clastic input and a near-shore environment of deposition. Geochemical data indicate the Cenomanian-Turonian
sequences in Sicily are characterised by higher source rock quality than equivalent facies in Tunisia. By comparison the Bahloul Formation in
northern Tunisia exhibits up to 14% TOC with an average value of 2%, and petroleum potential ranging between 2 and 50 kg HC/ton (El Euchi et
al., 2004).

Oil - source rock correlations based on stable carbon isotopes indicate a correlation between the oils of Nilde and Norma in the inverted Messinian-
Tortonian foredeep, the Bahloul Formation in Tunisia and the equivalent Bahloul facies in northeastern Sicily. The latter oils are characterized by
δC13 aromatic values close to Cenomanian-Turonian source rocks but saturate values are closer to an Early Cretaceous or Numidian Flysch age
(Oligo-Miocene). This possibly reflects a greater terrestrial input (Figure 7). The Numidian Flysch is not present in the inverted Messinian-
Tortonian foredeep. Although it likely occurs in the offshore thrust belt, as suggested by geophysical mapping it does not appear to be buried deep
enough to have generated hydrocarbons. A contribution from the Fahdene Formation (Early Cretaceous) cannot be ruled out.