MEDITERRANEAN-MIDDLE EASTERN ATLANTIC FAÇADE:MOLLUSCAN BIOGEOGRAPHY & ECOBIOSTRATIGRAPHYTHROUGHOUT THE LATE NEOGENE

We propose the definition of Atlantic pre-glacial Pliocene Molluscan Units and a critical comparison with the Mediterranean Pliocene Molluscan Units (MPMU1) of Raffi & Monegatti (1993). Our aim is to outline the extent and boundaries of the pre-glacial climatic zone (in the sense of Hall, 1964) by means of molluscan proxy data. This approach enables to demonstrate that the latitudes between 38° and 40° both through the pre-glacial Pliocene, before 3.0 Ma, and at the Present-day, mark the transition between two different climatic marine zones. These latitudes marked the boundary between the tropical and subtropical zones in the pre-glacial Pliocene, whereas they correspond to the subtropical-warm temperate transition in the Present-day. A similar pattern is recognizable at about Latitude 50° North which in the present-day approximates the boundary between the warm-cool temperate climatic zones and in the pre-glacial Pliocene marked the boundary between the subtropical-warm temperate zones. This setting has been linked to the long-standing debate on marine latitudinal diversity gradients and their explanations. Productivity as a consequence of temperature regime triggered by solar input and geographic-oceanographic setting appear to be the basic factors (Roy et al., 1998).