Deep-sea ostracods as indicators of palaeoceanographic changes: a case history from the middle–late Miocene of southern Italy (Central Mediterranean)

ABSTRACT The middle–late Miocene palaeoceanography of the Central Mediterranean was investigated using bio-chronostratigraphically constrained (estimated ages are based on plancktonic foraminifers) ostracod faunas from the Tremiti Islands and the Hyblean Plateau (southern Italy). Specifically, differences and similarities between the hydrographical evolution of the two study areas, inferred from the ostracod record, are herein used to provide new insights into the evolution of the Mediterranean deep-water circulation. Ostracod assemblage compositions suggest a simultaneous progressive trend from deep thermospheric towards psychrospheric conditions in both the areas during the Langhian. However, this trend seems to have developed fully only in the Hyblean Plateau. Notably, the first sign of an oceanic deep water-mass supply is shown by the almost synchronous entry of the upper psychrospheric genus Agrenocythere in the middle Langhian. The youngest reliable evidence of deep oceanic influences (common occurrence of Agrenocythere ) in the Central Mediterranean comes from the Tremiti Islands and dates back to the earliest Serravallian. Similarities between the two study areas suggest large-scale modifications in the Central Mediterranean deep basins. This hypothesis is discussed in the context of the global middle Miocene oceanographic scenario.