Relationships between the stratigraphic successions outcropping in the area of Nocara and Serra Maggiore (southern Apennines, Calabro-Lucanian boundary) and the Miocene evolution of the Lagonegro basin.

The southern Apennines are a NE verging fold-and-thrust belt derived from the deformation of the western continental edge of the Adria plate (D'ARGENIO et alii, 1980). The thrust belt formed during the late Oligocene-Pleistocene time interval and involved sedimentary rocks derived front basins formed in different geodynamic and paleogeographic domains. According to the classical restorations of the pre-orogenic paleogeography of the southern Apennines, the Adria plate was characterized by neritic carbonate platforms afternanting with pelagic basins; platforms and basins are variable in number and position according to different paleogeographic models (SELLI, 1962; OGNIBEN, 1969; SCANDONE, 1972; D'ARGENIO et alii, 1973, 1975; IPPOLITO et alii, 1975; PESCATORE & TRAMUTOLI, 1980; SGROSSO, 1988, 1994; MOSTARDINI & MERLINI, 1986; PESCATORE, 1988; PESCATORE et alii, 1999; PATACCA et alii, 1990, 1992a; MARSELLA et alii, 1995). Stratigraphic and structural relationships among successions outcropping in the area of Nocara and Serra Maggiore (calabrolucanian boundary) have been investigated and three different successions have been identified. The Nocara Succession, made up of: a) Langhian conglomerates and siliciclastic turbidites (Conglomerati di Nocara Formation); b) Burdigalian sandstone and marl turbidites (Arenarie di Colle delta Cappella Formation); c) Middle Cretaceous to Oligocene varicoloured clays and mart with calcarenites and marly-limestones (Argille Varicolori Formation). The Conglomerati di Nocara Formation lies paraconformably on the Arenarie di Colle delta Cappella Formation, the latter lies conformably on the Argille Varicolori Formation. The Timpone della Castagna Succession, made up of: 0) Burdigalian volcaniclastic sandstones and marls (Tufiti di Tusa Formation); b) Middle Cretaceous to Oligocene varicoloured clays and marls with calcarenites and marly-limestones (Argille Varicolori Formation). The Tufiti di Tusa Formation lies conformably on the Argille Varicolori Formation and grades into the overlying Numidian quartzarenites. The Serra Maggiore Succession, made tip of: a) Langhian Numidian sandstone (Flysch Numidico Formation). In several areas located north-northwest of the study area the Flysch Numidico Formation lies on Upper Cretaceous-Oligocene marls and shales with calcarenites and calcirudites (Flysch Rosso), and grades into overlying Middle to Upper Miocene turbiditic siliciclastic and calciclastic deposits (Serra Palazzo Formation). The deposits forming these successions have previously been related to different paleogeographic domains, namely the Sicilide basin, the Lagonegro basin and the Irpinian basin. Stratigraphic studies point out the analogies between the studied successions and the Lagonegro basin successions analysed by PESCATORE et alii, 1999. According to PESCATORE et alii, 1999, the Lagonegro basin was a pelagic basin interposed between two neritic carbonate platform domains (the western Apennine platform and the eastern Apulian platform) characterized by the following successions: a) Triassic to Oligocene pre-orogenic siliciclastic, carbonate and siliceous successions (i.e. Middle Cretaceous to Oligocene Argille Varicolori and Upper Cretaceous to Oligocene Flysch Rosso); b) Upper Oligocene-Lower Miocene siliciclastic, volcaniclastic and calciclastic successions (i.e.Tufiti di Tusa and correlated successions); c) Langhian to Tortonian foredeep and syntectonic siliciclastic and calciclastic successions (i.e. Flysch Numidico, Serra Palazzo Formation, Flysch di Gorgoglione and correlated successions). Since Lower Miocene time this basin was characterised by a complex tectonic setting, comprising an eastern foreland basin area with a depocentre migrating eastward (Flysch Numidico and Serra Palazzo Formations) and a western deformed area characterised by syntectonic basins (Conglomerati di Nocara and Flysch di Gorgoglione Formations). In the study area structural data support a complex polyphase tectonic evolution of these successions. Miocene deposits and their substratum are affected by intense deformation resulting from folding and thrust-related shear. The structure of the study area is characterised by the superposition of the Argille Varicolori Formation (Nocara Succession and Timpone la Castagna Succession-Lagonegro Basin's western margin and basinal successions) onto the Flysch Numidico Formation (Serra Maggiore Succession-Lagonegro Basin's eastern margin succession). Furthermore, the structure is characterised by the presence of a box fold associated with a triangle zone (Nocara Succession). Structural analysis point out the presence of: a) a first folding phase, affecting the Arenarie di Colle della Cappella Formation (F1 -close folds); b) a second folding phase, affecting both the Arenarie di Colle della Cappella Formation and the Conglomerati di Nocara Formation (F2-open folds trending N 140+/-10), refolding F1 folds and associated with the evolution of the triangle zone; c) a third folding phase affecting all the successions outcropping in the study area (F3-open folds trending N 40 10), responsible for the development of dome-and-basin structures; d) high angle faults, probably Pliocene and/or Quaternary in age, related to the third folding phase and responsible for the pop-up tectonic extrusion of the Serra Maggiore Succession.