Euthecosomatous pteropods as paleohydrological and paleoecological indicators in a Tyrrhenian deep-sea core

Abstract

Three assemblage zones could be recognized in a core from the northern Tyrrhenian Sea. The lowest zone is characterized by the absolute dominance of Limacina retroversa, the middle zone by the occurrence of Diacria trispinosa and the upper zone, representing the Holocene, by a diverse fauna with species like Cavolinia inflexa and Styliola subula. Paleohydrological interpretation indicates that the assemblage zones reflect major shifts in the position of water masses, in particular the expanding influence of eastern Mediterranean waters and the transitional to subtropical water masses of the eastern North Atlantic Ocean. The presence or absence of uncommon to rare pteropod species is of paleoenvironmental significance as well. Paleotemperature reconstruction, based on protoconch volume measurements of Clio pyramidata, indicate a rise in seawater temperature of some 4 to 5°C from glacial to post-glacial times. Comparisons with pteropod data from the literature, especially from the Adriatic Sea, make it clear that similar ecological changes can be observed in detail in different parts of the Mediterranean Sea. An ecostratigraphic zonation, the Quaternary Mediterranean Pteropod zonation (Q.M.P.T.), is therefore proposed.