Abstract

The geology of a very complex sector of southern Apennines is described in this paper. The sedimentological and tectono-stratigraphic features of Miocene and Pliocene sinorogenic successions and a new geological and structural field survey allowed to better define the timing of the tectonic evolution and the stacking pattern of the units of this portion of the Apenninic chain. The study area is comprised between Picentini Mts. and Daunia Mts., located from the Molise-Sannio to the Lucania-Campania segments of the outer thrust-belt. From Northeast to Southwest, six regional tectono-stratigraphic units are recognised: a) Vallone del Toro Unit (Basso et alii, 2001), constituted by basinal evaporitic and pelitic sequences, ranging in age from Middle-Late Tortonian to late Messinian; b) Daunia Unit (Pescatore et alii, 1996a, 1996b), composed by basinal and shelf margin facies, ranging in age from Oligocene to late Messinian, and tectonically lying on the Lower-Middle Pliocene deposits (Ariano Unit); c) Fortore Unit (Pescatore et alii, 2000), characterized by basinal facies, ranging in age from Late Cretaceous to Langhian (this unit overthrusts on the Daunia Unit); d) Frigento Unit (Sannio Unit p.p.) (Di Nocera et alii, 2002), made up of basinal and shelf margin facies, ranging from Triassic to Middle Miocene (this unit overthrusts the Fortore Unit and Daunia Unit); e) Cervialto-Terminio-Tuoro Mts. Unit, composed by carbonatic shallow water facies, interpreted as a fragment of the Southern Apenninic platform ("Campano-Lucana" platform), ranging from Late Jurassic to Paleogene (tectonically lying onto the Frigento Unit); f) Sicilide Unit (Ogniben, 1969), consisting of basinal facies, and ranging in age from Late Cretaceous to Langhian (the unit over-thrusts on both Cervialto-Terminio-Tuoro Mts. Unit and Frigento Unit). The a) to d) units belong to Lagonegro-Molise basinal domine; the f) unit belongs to Neo-Tethys basinal domain. Siliciclastic sequences represent the deposits of wedge-top basins, ranging in age from Middle Miocene (Pescatore et alii, 1970) to Pliocene, such as the Irpina Supersynthem, formed by the Castelvetere Synthem (Serravallian-Tortonian) and by the Villamaina Synthem (Tortonian-Early Messinian), the Altavilla Super-synthem (late Messinian), and the Ariano Supersynthem, formed by the Baronia Synthem (Early Pliocene) the Scompitella synthem (Early-Middle Pliocene) and the Sferracavallo Synthem (Middle Pliocene). Structural complexity seems to characterize the whole orogenic evolution of the ENE-verging fold-and-thrust belt system, but the major imbrications result from the post-Messinian thrusting and refolding with breaching (Butler, 1987) of more ancient structures. In the central sector of the Irpinia, the presence of duplex and successive structures (Apulian thrust system, Lentini et alii, 1990) is testified by the presence of the Inner Apulian Platform, encountered at a depth of ca. 500 m. The Lagonegro-Molise basin units tectonically overlie the buried Apulian Unit; their assemblage results from the breaching developed after the duplexing of the Apulian unit. Finally, the belt is widely affected by Plio-Quaternary strike-slip and extensional faults.

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