ABSTRACT: Source Rock Distribution Models of the Periadriatic Region

Enzo Zappaterra

The regional geology of the Periadriatic region can be expressed in terms of three Upper Triassic-Paleogene sedimentary sequences, each reflecting a particular sedimentary-tectonic setting and a specific paleogeographic evolution. These sequences are designated carbonate paleogeographic sequences (CPS).

Sequence A, the platform sequence, comprises thick tidal and subtidal platform carbonates of Upper Triassic to Paleogene age. Evaporites may locally occur in the lower part of the sequence. Sequence A indicates stable sedimentation and platform growth under uniform environmental conditions. It is distributed in northwest Sicily, Apulia, central and southern Apennines, Friuli, Istria, Dalmatia, and the Dinarides.

Sequence B, the platform-to-basin sequence, includes a lower platform unit of tidal-subtidal carbonates (Upper Triassic-Liassic) and an upper basinal unit of pelagic carbonate muds, marls, and cherts (Liassic-Paleogene). Sequence B reflects the breakup and foundering of carbonate platforms and the development of a new paleogeography characterized by a platform to basin morphology. It defines the time of onset of regional subsidence and tensional tectonics. Sequence B characterizes parts of onshore Sicily and the Ragusa area, the Umbria-Marche basin and the Tuscan area (northern Apennines), parts of the central and southern Apennines, most of the southern Alps, the Po basin, and portions of the Adriatic Sea margin.

Sequence C, the basin sequence, is composed of pelagic carbonate-siliceous rocks deposited in persistent deep-water basins from the Upper Triassic to early Tertiary. Sequence C represents continuous sedimentation in deep-water basins with slow deposition. Sequence C includes the Imerese (Sicily), Lagonegro (southern Apennines), and Budva (Yugoslavia-Albania) basins.

The relation between carbonate source rocks and type of sequence makes it possible to rank the different areas of the Periadriatic region in terms of their source-rock potential and, ultimately, of their petroleum resources.

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