Late Neogene Radiolaria and Mediterranean Paleoenvironments

Abstract

Although widespread in Mediterranean Miocene sediments, radiolarians occur in only a small proportion of the Pliocene and Quaternary sediments of that region. The major factor responsible for their occurrence seems to be increased biological productivity. Preserved late Neogene assemblages are highly diverse (we estimate that there are about 100 species that occur in substantial numbers) and contain strong paleoenvironmental signals that have scarcely begun to be tapped. Pliocene and Quaternary assemblages are somewhat more diverse than Miocene ones and are more diverse in the Western than in the Eastern Mediterranean. In the Western Mediterranean, Pliocene assemblages are more diverse than those of the Messinian. Assuming that taxonomic groups present or enhanced in Messinian samples are analogous to similar groups in the present-day plankton, trends of cooling, shallowing, and increasing productivity can be interpreted through the Monte Giammoia section, Sicily. Analysis of dominance in the assemblages yields results that cannot yet be interpreted satisfactorily.