Late Messinian Lago-Mare ostracods and palaeoenvironments of the central and eastern Mediterranean Basin

The ostracod assemblages with Paratethyan affinity from several late Messinian Lago-Mare deposits located in Italy and Crete (Greece) have been examined and the community analyses (number of species, Margalef and Shannon-Wiener indexes) and auto/ synecological analyses have been performed on them. The results show that, generally, in the lower portion the post-evaporitic Messinian was characterised by unstable environments, which hosted poor ostracod communities characterised by low diversity, while in the upper portion the environmental conditions were more stable, allowing the subdivision of the environment hyperspace in several different niches and, thus, supporting high-diversity ostracod communities. Anyway, the correlation of the boundary between low- and high-diversity ostracod assemblages through the studied successions has shown to be heterochronous, probably because it is due both to local and regional factors. A more detailed palaeoenvironmental reconstruction across the late Messinian Lago-Mare successions showed that, while in the lower portion the palaeoenvironments are rather disomogeneous, even if investigated in nearby sections, in the upper part a general trend towards a deepening and freshening followed by a new salinity increase and depth decrease has been recognized. The palaeoenvironmental variability of the lower part probably was related to the superimposition of local factors on global climatic forcing, while in the upper part the high amplitude insolation peaks drove the palaeoenvironmental changes at a regional scale.