A three-dimensional high resolution sequence stratigraphic model of an Ypresian nummulitic carbonate ramp and organic-rich basin is presented based on outcrops in Central Tunisia. The sedimentation pattern is influenced by the interplay of different orders of variations in eustatic sea-level (third to fifth order), the pre-existing palaeotopography, and probably some synsedimentary tectonism (differential subsidence). Time-equivalent rocks deposited in a comparable structural and depositional setting along the northern margin of the African plate are hydrocarbon bearing (Tunisia and Libya). This example may thus serve as an outcrop analogue for this petroleum system, providing valuable information on the sub-seismic-scale distribution pattern, geometries and heterogeneities of both the reservoir and source rock facies. The studied outcrops cover an area of 10 by 20 km where present-day valleys provide three-dimensional access to the rocks. In addition, the transition from the inner/mid-ramp, with nummulitic reservoir facies, to the carbonate source rocks in the basin is exposed in continuous outcrops. This transition takes place in about 3 km, a distance generally beyond the resolution of well spacing. Based on the physical tracing of beds, and the recognition of three orders of depositional sequences (third to fifth) a high resolution time framework is constructed. The accumulation of large nummulites (best reservoir facies) is stratigraphically controlled, and occurs in the transgressive phases of the landward-stepping fourth order cycles (overall transgression). Carbonate production was at that time so high that aggrading geometries are observed during these transgressive pulses. Our observations show that size, morphology and reproduction strategy of foraminiferal assemblages and, particularly, nummulites and Discocyclina , are related to changes in water depth and, consequently, in accommodation space. A regional east–west cross-section shows significant thickness variations of the Ypresian succession that were probably controlled by synsedimentary differential subsidence. The detailed, sub-seismic-scale, geometrical information on stratal patterns and lateral facies change are quantified, and used in a 3D numerical stochastic modelling (HERESIM) of this petroleum system.

The regional Cenomanian-Turonian (C/T) structural framework of surface and subsurface coupled with subsidence data inferred from palegeographic and organic-rich C/T isopachs map, generated in this work, from several basins, wells and outcrops of Tunisia and eastern Algeria was investigated and provide constraints on the structural and sedimentary evolution of this part of the southern Tethyan margin during the C/T times. La réduction des zones emergées depuis la Cénomanien déduit de la carte paléogéographique est mis en évidence.L'évolution globale est également amplifiée par les mouvements diapirique du Trias créant des rim-synclines subsidents, où les faciès riches en matière organique ont prévalu.

Structural interpretations of seismic sections crossing the Tell area in Tunisia, allow us to outline the structural style of the subsurface along the thrust front of the Numidian ''nappe'' and its relationships with the substratum north of the Middle Mejerda valley. The seismic interpretations show a structural style characterized by large thrust sheets detached over the Triassic salt, whereas the autochthonous cover is affected by inherited faults and tilted blocks. These inherited faults are connected at depth on the major ''décollement'' level represented by the interface Triassic salt/Mesozoic-Cenozoic cover. This autochthonous Atlas type cover recorded the Eocene Atlas compressional event outlined by the angular unconformity of the Oligo-Miocene on top of folded Cretaceous strata. Seismic interpretation shows also the occurrence of important halokinetic movements deforming both the autochthonous and allochthonous series. Two types of diapirs can be distinguished: the first ones cutting the autochthonous sedimentary cover, the second ones the Tellian sheets specially the Numidian ''nappe'' which is the uppermost tectonic unit of the Tellian belt. These latter Triassic levels have pierced the allochthonous cover after the ''nappes'' emplacement i.e. after the Langhian and during the Late Miocene compressional events. Otherwise, Triassic salt is incorporated as sole thrust level beneath the Numidian ''nappe''. A regional structural transect crossing the whole Tunisia thrust belt from the Tell to the southeastern foreland and the Zaghoaun thrust-fault allows us to illustrate the overall structural style of the Domain. It outlines the occurrence, beneath the upper-most Tellian structural level (Numidian) of imbricated units issued from duplexing of the sedimentary cover. It appears that the Numidian ''nappe'' detaches over Middle-Late Eocene shales which represent the upper-most ''décollement'' level. The Triassic salts locally exposed at the base the Numidian ''nappe'' are incorporated mechanically during the southward gliding of the ''nappe'' above the duplex structures.

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