Ostracod faunas and brackish-water environments of the late Messinian Sapigno section (northern Apennines, Italy)

摘要

The sediments and ostracod assemblages from a small lacustrine basin located in the Montefeltro area (Sapigno Syncline, Romagna-Marche Apennine, Central Italy) have been studied in detail from a section covering a broad interval spanning the Late Messinian post-evaporitic sequence. The latter consists of a non-marine, mainly terrigenous succession with molluscs and brackish-water ostracods; it represents the Lago-Mare phase s.s. and is interpreted as shallow- to relatively deep-water lacustrine deposits characterized by a low salinity with occasional interactions with fluvial and littoral processes. Rich and diverse ostracod assemblages occur throughout the studied succession. Thirty species were recognized, which characterize a Loxocorniculina diaforovi Fossil Assemblage widespread in the western Mediterranean during the latest part of the Messinian. It is a residual assemblage of a non-marine fauna inhabiting hypohaline environments and testifies to the presence of large, interconnected, brackish-water bodies (Lago-Mare) along the margins and in the depths of a Mediterranean basin isolated from the World Ocean. The ostracod faunas have Paratethyan affinities but only a few species are common to both the western Mediterranean and the eastern basins of Paratethys.