Seismic analyses and detailed well-log correlations have been used to define the depositional patterns and the relative timing of thrust movements in the highly mobile Peri-Adriatic Foredeep, a gas-bearing basin of Pliocene age in NE Italy. Due to the high rates of sedimentation and subsidence, up to 8,000 m of mostly deep-water clastics were deposited in the foredeep in the Marche-Abruzzo area during the Pliocene-early Pleistocene.

Three phases of foredeep evolution can be recognised. In the first phase, during which there was little structural activity, a sandy turbidite system of regional dimensions (the Cellino Turbidite System) developed on a flat, stable substratum. Discrete sand-bodies belonging to this system can be traced over distances of up to 80 km. This turbidite system is a key unit in the analysis of the foredeep. The rapid deposition and burial of organic-rich sediments favoured the generation of biogenic gas.

The second phase of foredeep evolution coincided with the onset of structural deformation. Sediments are mainly deep-marine shales and minor turbidite sandstones, which were deposited during a period of almost continuous tectonic activity. A major eastward migration of the deep-marine depocentre then occurred. In the study area, this phase is represented by a series of closely-spaced local unconformities which can be correlated eastwards with a major late Pliocene turbidite system. The high frequency of the unconformities is a distinctive feature of this interval.

The third phase was characterised by thrusting in the eastern part of the foredeep and by the development of a piggy-back basin. During this phase, shallow-water, coarse-grained deltas replaced the deep-water turbidite systems. Accommodation space for the coarsegrained deltas was provided to begin with by rapid subsidence. The progressive decrease in accommodation resulted in delta progradation eastwards and ultimately in the infilling of the foredeep.