Significato paleoambientale e cronostratigrafico delle mammalofaune pleistoceniche della Sicilia in relazione all'evoluzione peleogeografica

Abstract

The location of Pleistocene mammal-bearing deposits of Sicily, their sedimentary environments and mammal faunal associations are here presented. The purpose is to outline the paleogeographic setting which influenced the dispersal and the preservation of the Pleistocene mammal- faunas of the island. In the recent years isoleucine age determinations and new findings in the Hyblean Plateau provide the cronologie and stratigraphic evidence to definitively discredit previous biostratigraphic schemes concerning Pleistocene mammals of Sicily. These schemes were based on the assumption of the phylogenetic derivation of the elephant of most reduced size, Elephas falconeri Busk, from that of less reduced size, E. mnaidriensis Adams, which is a direct descendent of E. antiquus. New findings assigned an older age to the E. falconeri Busk faunal association (early Middle Pleistocene) and a younger age to the E. mnaidriensis and Hippopotamus pentlandi faunal association (late Middle Pleistocene - Upper Pleistocence). New findings provide also a better knowledge of the taphonomy of the mammal-bearing deposits, traditionally linked to karstic environment. The data here produced provide a palaeogeographic outline of Sicily derived from the stratigraphic and taphonomic characters of the Pleistocene mammal-bearing deposits. These data are: 1 ) The settlement of the deposits displays different palaeogeographic conditions and different faunal associations in western-south eastern and north eastern Sicily, respectively. 2) The taphonomic setting in the different sites shows that the bones accumulated in different environments, which are: colluvial and alluvial deposits, cave and fissure-fillings deposits, lacustrine and coastal plain deposits, littoral environment. Palaeoenvironmental conditions provide quantitative differences in the faunal composition of different deposits, which belong to the same geological time span. 3) The faunal associations have palaeoenvironmental and stratigraphic significance 4) The older faunal association, containing Elephas falconeri and endemic micromammals, occurs in the Hyblean Plateau and in the Palermo Mountains; the younger mammal faunal association, containing Elephas mnaidriensis and Hippopotamus pentlandi associated with cervides, bovides and carnivora, is widespread in the island. 5) The present knowledge about the Pleistocene palaeogeographic evolution in the Strait of Messina area makes it possible to recognize a land connection between Sicily and southern Calabria during late Middle- Pleistocene and early Upper Pleistocene. 6) Data are lacking concerning the dispersal route of the older E. falconeri mammal faunal association.