Integrated biostratigraphy and palaeogeographical interpretations of Upper Jurassic-Lower Cretaceous (Callovian-Berriasian) successions are synthesised on the basis of published data and our recent investigations of key sections from the "Tunisian Dorasale" (TD) and "Tunisian Trough" (TT) domains of northern Tunisia. After a revised biostratigraphy had been proposed for the "rosso ammonitico" series, bed-by-bed sampling led to a radiolarian-based first direct dating of the partly coeval biosiliceous series in the TT. Upward within the Jurassic column, an integrated biostratigraphy (ammonites, calpionellids and associated biomicrofacies) allowed precise biozonation for the Kimmeridgian-middle Berriasian interval. The heterogeneity of the Late Jurassic facies in northern Tunisia is the result of two main geodynamical and palaeogeographical events. The first corresponds to the fragmentation of the initial Early Jurassic platform linked to Tethyan rifting. The second event, coeval to the radiolarian-bearing series of the TT, is expressed by a significant deepening in north-west Tunisian palaeoenvironments. During Kimmeridgian -Tithonian times, previous troughs evolved back into carbonate platforms. Within the Maghrebian Belt, Upper Jurassic-lowermost Cretaceous series comprising three major facies groups are easily correlated; minor differences in age are interpreted as due to local tectonic control. Regional correlations confirm, on the one hand, a common geological history for the external segments of the African margin and, on the other hand, a distinct palaeogeographical evolution of the inner domain including the "Dorsales calcaires" and ancient massifs, both being separated by intermediate flysch zone segments.

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Integrated study was carried out on the Jeffara basin in order to understand and discuss the geometry and the key levels as well as Petroleum System elements on the Jurassic strata. The studied area lies as N140-130 trending down faulted area roughly parallel to the coastline; it was developed mainly in response stage of Tethyan rifting. The subsurface data reveal that most of the structuring is amplified by halokinesis and the salt piercement of the entire sedimentary cover in the southeast area. The Mrabtine Formation, which is represented by a mixed siliciclastic and carbonate deposits, is considered to be the best Jurassic potential reservoir rock in the Jeffera basin. The Callovian shales appear to contain the best potential for source rock off all units in the Jurassic, showing poor to good TOC contents (up to 3.27% TOC) and good petroleum potential up to 10 kg of HC/ton of rock. The kerogens are mainly type II algal material and mix type II and III with locally higher type III organic material in El Bibane and Jerba area. Several prospects and leads have been identified at the top of the Mrabtine Formation, these structures are extensional fault related (horsts or tilted fault blocks) with a NW-SE orientation. The northern part of the Jeffara basin shows several attractive fault related traps but sedimentological and stratigraphic studies indicate that there would be a risk of poor reservoir characteristics, a lack of source facies and top seal. The southern domain contains fewer structures and leads but more attractive plays with the proven hydrocarbon accumulations of the Ezzaouia and El Biban Fields.

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