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ABSTRACT: Oil and Gas Occurrences vs. Geodynamic Evolution in the Southern Apennines (Italy)

P. Casero, A. Rossato, F. Roure, R. Vially

The present architecture of the southern Apennines results from the Neogene continental subduction of the Apulia margin (part of North Africa margin).

An allochthonous complex is formed by the low-angle, large-scale, east-vergent tectonic stack of Triassic to upper Miocene (Messinian) units. The rocks represent both a shelf carbonate domain (Apennine platform) and a deep marine domain (Lagonegro-Molise basin). They are emplaced as a nappe during uppermost Miocene (Messinian) to lowermost Pliocene. They are transported to the northeast onto the flexed inner part of the Apulia platform (Mesozoic to late Miocene shelf carbonate series).

During the middle-upper Pliocene, the inner Apulia carbonate margin (intermediate platform) was thrust against the outer Apulia domain (overthrust belt). Pliocene-Quaternary syntectonic clastic series were deposited in the flexural basin developed to the east of the Apenninic allochthon outer ramp and also in piggyback basins carried on top of the allochthon.

Oil occurrences are confined to the top of the platform carbonates. Discoveries have been made in (1) compressional structures of the overthrust belt (outer margin of the inner Apulian Platform), (2) late-stage compressive folds in the outer slope of the foredeep, and (3) slightly inverted structures of the foreland margin.

Gas accumulations at the top of platform limestones occur only in antithetic fault block traps or in slightly inverted structures of the foreland. The most important and frequent biogenic accumulations are in clastic rocks of the foredeep, beneath and to the east of the frontal ramp of the allochthon.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990