Note illustrative della Carta Geologica d’Italia (scala 1:50.000), Foglio 378 "Scanno".

The area covered by the geological map “Foglio 378 Scanno” is located in the central sector of the Apennine chain. It includes the NE sector of the “Marsica” region (Almagià, 1910) and the western part of the Peligna valley. The northern part of the “Abruzzo, Lazio e Molise” National Park and a small portion of the “Majella” National Park are also included in the study area. The geography of the area is typified by NW-SE and N-S trending ridges, divided by narrow valleys. The height of the ridge is around 1800 m asl., with highest peaks exceeding 2200 m. asl. This gives the region an overall high relief that is contrasted with relative low plains along the boundaries of the study area. From the geological point of view, the area is located in the axial sector of the Apennines. A thrust belt started developing in the Neogene, following an arch geometry that reflects the complexity of the deep structures, which is still not well understood and debated. The thrusts and folding stacked one over each other successions, belonging to different paleogeographical domains. Since the Late Miocene, and throughout the Pleistocene, the area experienced regional uplift and extensional faulting, driving the initial phases of morphogenesis. This map area shows a complex stratigraphic setting, having witnessed several different sedimentary environments throughout the Mesozoic and the Cenozoic. Based on the sedimentary environment and in respect of the main tectonic events occurred in the area, stratigraphic successions can be divided into: - Pre-orogenic Meso-Cenozoic marine successions; - Syn- and late-orogenic Neogene marine successions; - Post-orogenic Quaternary continental successions. Each of these successions are complicated and have been further described. Sediments related to a carbonate platform, slope, and pelagic basin environment, influenced by the detritic discharge coming from the reef are grouped as Pre-orogenic successions. Lithologies related to these environments out-crop in the area in well defined sectors, bounded by main tectonic elements and divided from one another by narrow corridors of syn-orogenic deposits. The outcrops are then highly partitioned and, as a result, the reconstruction of the relationship between the different environments is very difficult to determine and is often impossible. Moving roughly perpendicular to the structures, in a SW-NE direction, inner carbonate platform sediments are at first encountered in the mountains on the western edge of the map, from the Fucino plain to the Pescasseroli area. These carbonates present monotonous features, on a span of time that extends from the Triassic(?) - Lower Jurassic to the Upper Cretaceous. These are unconformably overlain by miocenic calcarenites, which are related to the carbonate ramp environment. Moving to the NE, within the central part of the area, the “Montagna Grande” ridge is dominated by detritic and reef related deposits which extend from the Lower - Middle Jurassic to the Upper Cretaceous. Although some big facies variations are recognized in the stratigraphic series, the main features remain constant throughout the entire time span. On the eastern flank of the ridge some sediments that are related to a more distal and deep-sea environment crop out. Slope to basin sediments crop out largely on the NE quadrangle, on the “Mt. Genzana – Serra Sparvera” ridge. They span from the Lower Jurassic to the Paleogene. Micritic, thin bedded, mudstone are interbedded within thick bedded, detritic, limestone, denoting the strong influence that the carbonatic slope still exerted on this area. In this quadrangle, carbonatic ramp calcarenites, Miocene in age, lie unconformably on different formations of the pelagic sequence. A marly formation is present at the top of the Cenozoic sequences, marking the end of the carbonatic deposition and the beginning of the siliciclastic, syn-orogenic environment. Syn-orogenic successions are constituted by terrigenous sediments, typically silt and clay, with few arenaceous strata, Upper Miocene in age (Tortonian - Messinian, both before and after the “salinity crisis”). These sediments crop out in the valley interposed within the main carbonatic ridges. In the area of Anversa degli Abruzzi, in the siliciclastic succession, a small outcrop of gypsum is present. Late-orogenic deposits are few and scattered in the area, but those present are made of clastic, conglomeratic deposits related to piggy-back. They are Upper Miocene in age (Upper Messinian, post “salinity crisis”). The stratigraphy of the area ends with post-orogenic successions that include the Quaternary continental deposits cropping out in the area. These sediments range in age from the Upper Pliocene to the Holocene. Several synthems and many different lithofacies have been recognized in the area. This makes the stratigraphical setting complex, according to a long Quaternary evolutionary history of this portion of the chain. The variability of the stratigraphic sequences, especially those related to the pre-orogenic successions, testify for active tectonics during the sedimentation, which has driven the diversification of depositional environments. In the Upper Miocene tectonic processes initiated the formation of the chain by means of folding and thrusting. The main elements show orientations that range between NW-SE and N-S and trend both NE and SW. Compression is followed, in the Lower Pliocene, by transpression, mainly developed along NNW-SSE alignment. Currently the principal elements referring to this tectonic phase are recognized on the western flank of the M. Marsicano and along the Sagittario River Valley – Masserie Valley – Serra Sparvera ridge alignment. Extensional tectonics affected this area beginning in the Upper Pliocene through the Holocene. The activity of these elements, striking in a range of orientation from NNW-SSE to N 70° W, is responsible, among other things, for the development of intermountain basins like the Fucino Plain.