An evaporitic limestone–gypsum succession, belonging to the Evaporiti di Monte Castello Formation, is recognized in the late Messinian (Upper Miocene) of the Irpinia–Daunia Mountains in the Southern Apennines arc (Southern Italy). This unit is formed by diatomaceous marls, massive and laminated evaporitic limestones, and by primary and clastic gypsum. Detailed stratigraphical, sedimentological and strontium geochemistry data has permitted reconstruction of stratigraphic and facies relations of gypsum deposits, depositional environment and basin evolution. Genetically related gypsum lithofacies can be grouped into two facies associations. The autochthonous gypsum facies association consists of shallow water selenitic, acicular and laminated gypsum and is characterized by the absence of high-energy sedimentary structures. The redeposited clastic gypsum facies association consists of shallowto deeper-water finegrained laminated gypsum, gypsarenites, pebbly gypsarenites and gypsrudites, showing common features of resedimented deposits. Nodular structures occurring in the laminated gypsum lithofacies seem to be mostly related to late diagenetic processes. The sedimentary evolution during the evaporative phase was characterized by a gradual increase in salinity until gypsum precipitated; then the sedimentary conditions in the basin were characterized by almost homogenous salinity conditions, and influenced by events of gypsum reworking and resedimentation probably related to flooding episodes and local tectonic activity. The gypsum was deposited from mainly marine brines, based on their Sr isotopic compositions. This sedimentary series is an equivalent of the Lower Evaporites of other parts of the Mediterranean. The Messinian Monte Castello Formation evaporites represent an uncommon type of evaporitic succession, probably developed in a extensional setting in a basin located along the Apulian foreland ramp, in contrast with the northern Apennines and Sicilian basins (e.g. Vena del Gesso, and Caltanisetta basins), which are considered to be thrust-top basins of the Apennine–Maghrebian foreland basin system. An important episode of evaporitic deposition during the Messinian stage, related to the so-called ‘salinity crisis’ (Selli 1960; Hsu et al. 1973a, b), further complicated the very complex Late Miocene geological context of the Mediterranean region (Fig. 1), characterized by the advanced stage of collisional coupling between the African and the Eurasian plates (Cavazza & Wezel 2003). During the Messinian salinity crisis, the Mediterranean basins episodically desiccated and large volumes of evaporitic deposits precipitated on the floor of deep marine basins (Hsu et al. 1973a, 1977; Kastens & Mascle 1990), as well as on their shallower, marginal portions. As a matter of fact, Messinian evaporite deposits crop out in a considerable number of localities around the Mediterranean Sea, such as Sicily (Decima & Wezel 1973; Schreiber et al. 1976; Butler et al. 1995, 1999), Southern Apennines (Di Nocera et al. 1975, 1981; Dazzaro et al. 1988; Matano et al. 2005), Northern Apennines (Vai & Ricci Lucchi 1977; Roveri et al. 2001, 2003), Southest Spain (Michalzik 1996; Riding et al. 1998, 1999; Playa et al. 2000), Northern Africa, Crete, Cyprus and Southern Turkey (Rouchy 1982). Messinian evaporitic deposition occurred in a series of smaller discrete basins, which were different in dimensions and form from the large pre-Messinian Mediterranean basins, characterized by open marine conditions. The initiation of the salinity crisis resulted mainly from tectonic processes, which progressively restricted and partly isolated the Mediterranean Sea from the Atlantic Ocean (Hodell et al. 2001; Vidal et al. 2002; Duggen et al. 2003; Krijgsman et al. 2004). High-resolution cyclostratigraphic studies show that the onset of the Messinian salinity crisis is dated at 5.96 + 0.02 Ma and is synchronous over the entire Mediterranean basin (Krijgsman et al. 1999). Some data are in contrast with this result, such as those referred to the Sicilian Maghrebides foreland basin, where the beginning of evaporitic deposition is considered to be diachronous over a period of at least 0.8 Ma by Butler et al. (1999). It seems that each evaporitic basin had its own tectonic and hydrologic history and hence a From: SCHREIBER, B. C., LUGLI, S. & BĄBEL, M. (eds) Evaporites Through Space and Time. Geological Society, London, Special Publications, 285, 191–218. DOI: 10.1144/SP285.12 0305-8719/07/$15.00 # The Geological Society of London 2007. different history of evaporite deposition; as a consequence, a full understanding of the Messinian evaporites must await resolution of the tectonic history of the Mediterranean basin and its component sub-basins (Hardie & Lowenstein 2004). The Messinian was also a period of widespread and short-lived tectonic activity along the contractional fronts from Sicily and Apennines to Crete and Cyprus (Fig. 1). The so-called ‘intra-Messinian tectonic phase’ caused thrusting, development of widespread unconformities and deposition of syntectonic coarse-grained sediments and reworked evaporites (Decima & Wezel 1973; Elter et al. 1975; Di Nocera et al. 1976; Torre et al. 1988; Patacca & Scandone 1989; Butler et al. 1995; Cavazza & De Celles 1998; Roveri et al. 1998, 2001, 2003, 2004). Two major Messinian sedimentary cycles separated by a deeply incised erosion surface are usually recognized in the Mediterranean basins. The classic Messinian composite stratigraphic succession exposed in Sicily starts with alternations of open marine marls and sapropels, laminated diatomites (‘Tripoli Formation’) and evaporitic limestones (‘Calcare di Base’), and passes into gypsum and halite (‘Lower Evaporites’). The ‘Upper Evaporites’ overlie an erosional unconformity and comprise gypsum and marls, and are in turn overlain by the Lago-Mare deposits of the Arenazzolo Formation (Ogniben 1957; Decima & Wezel 1973). In northern Apennines the Upper Evaporites are not present and two mainly terrigenous unconformity-bounded units form the post-evaporitic Messinian deposits (Roveri et al. 1998, 2001). The ‘Lower Evaporites’ (Gessoso-Solfifera Formation) are formed by mainly shallow-water facies in the Romagna and Emilia sectors (Vena del Gesso basin, Vai & Ricci Lucchi 1977) and by resedimented evaporites in the Marche and Abruzzi sectors of nothern Apennines (Roveri et al. 2003). These evaporitic sequences have been referred to wedge-top and foredeep depocenters of the Apennine foreland basin system (Roveri et al. 1998, 2001, 2003, 2004). In southern Apennines there are two main areas of Messinian evaporites outcrops (Fig. 2). In the Sannio–western Irpinia area the evaporitic deposits have been referred to two different units separated Fig. 1. Paleogeographic and tectonic reconstruction of the Mediterranean domains during Late Messinian (modified after Matano et al. 2005). Land areas and main thrusts distribution are from Cipollari et al. (1999a, b) and Ziegler (1999). The Mediterranean basin subdivision is from Riding et al. (1999, and references therein), Roveri et al. (2001) and Griffin (2002). Western Mediterranean areas are formed by basins characterized by deep or complete desiccation, followed by marine reflooding with scarce evidence of brackish Lago Mare onditions; central and eastern Mediterranean areas are formed by basins characterized by partial desiccation, with deep portions of the basin never desiccated, followed by widespread brackish Lago Mare conditions. F. MATANO 192