Geomorphologic evolution and neotectonics of the Sulmona intramontane basin (Abruzzi Apennine, Central Italy)

The Sulmona intramontane basin, elongated NW-SE according to the main tectonic structures of the area, is the easternmost of numerous tectonic depressions which characterize the inner part of Central Apennines. Although it is NW-SE trending, the basin contains oriented N-S and E-W tectonic structures just a few kilometres to the north and to the east. Such depressions have been formed during Middle-Upper Pliocene, after the end of the main tectogenetic phases of the Apennine chain. In order to outline the geomorphologic evolution of the area, detailed geological and geomorphologic investigations have been carried out, basing on both air-photo interpretation and field survey. The resulting framework is the following: a) formation of a half-graben depression (probably Upper Pliocene); b) formation of alluvial fans (Morrone area) (Lower Pleistocene); c) sedimentation in lacustrine-swampy environment (Middle Pleistocene); d) sedimentation of alluvial conglomerates (Sulmona surface) (late Middle Pleistocene - Upper Pleistocene); formation of alluvial fans and fluvial terraces (late Middle Pleistocene - Upper Pleistocene); e) deposition of recent and present-day alluvial sediments (Holocene). Tectonic activity, producing E-W and NW-SE trending faults, afected the area since half-graben formation up to present times. This sequence of events is also recorded in other similar depressions (Rieti, L'Aquila, Fucino) and may be considered representative of the Middle Pliocene-Quaternary evolution of Central Apennines.