The early Quaternary palaeobiogeography of the eastern Ionian deep-sea Teleost fauna: A novel palaeocirculation approach

Abstract

The early Quaternary stratigraphic and geographic distribution of teleostean fishes in the Ionian Sea (eastern Mediterranean) is examined based on the fossil otolith record. Through comparison between the western and the eastern Ionian early–middle Pleistocene deep-sea ichthyofauna, the stratigraphic distributions of nineteen taxa are revised. A new method of assemblage analysis is attempted, in order to discern the palaeoceanographic conditions prevailing at this time. The relative contributions of tropical, subtropical, temperate, and subpolar taxa to the surface, intermediate, and deepwater fish palaeofauna are calculated, using fossil material from Akrotiri (Kephallonia Island, Greece), Gerakas (Zakynthos Island, Greece) and Montalbano Jonico (Italy) sections, which span the Gelasian–Ionian time interval. Eleven distinct phases in the Ionian Sea palaeoceanographic evolution are distinguished, from prior 1.95 Ma to 0.61 Ma. Furthermore, a case study is conducted, to test the hypothesis that palaeoichthyofauna can be used to draw conclusions regarding the palaeocirculation patterns and their variability. In the Ionian Sea, the local production and/or Atlantic origin of the deep cold waters is registered already during the Gelasian. The presence of oceanic fish in the eastern Ionian can be explained by the existence of a strong anticyclonic gyre in the area during the early Quaternary, further indicating that the basin's geometry exhibited sufficient bathymetric variation to allow for the activation of the gyre.