Benthic Foraminiferal Assemblages and Rhodolith Facies Evolution in Post-LGM Sediments from the Pontine Archipelago Shelf (Central Tyrrhenian Sea, Italy)

Abstract

The seabed of the Pontine Archipelago (Tyrrhenian Sea) insular shelf is peculiar as it is characterized by a mixed siliciclastic–carbonate sedimentation. In order to reconstruct the Late Quaternary paleoenvironmental evolution of the Pontine Archipelago, this study investigates the succession of facies recorded by two sediment cores. For this purpose, benthic foraminifera and rhodoliths assemblages were considered. The two cores (post-Last Glacial Maximum in age) were collected at 60 (CS1) and 122 m (Caro1) depth on the insular shelf off Ponza Island. The paleontological data were compared with seismo-stratigraphic and lithological evidence. The cores show a deepening succession, with a transition from a basal rhodolith-rich biodetritic coarse sand to the surface coralline-barren silty sand. This transition is more evident along core Caro1 (from the bottom to the top), collected at a deeper water depth than CS1. In support of this evidence, along Caro1 was recorded a fairly constant increase in the amount of planktonic foraminiferal and a marked change in benthic foraminiferal assemblages (from Asterigerinata mamilla and Lobatula lobatula assemblage to Cassidulina carinata assemblage). Interestingly, the dating of the Caro1 bottom allowed us to extend to more than 13,000 years BP the rhodolith record in the Pontine Archipelago, indicating the possible presence of an active carbonate factory at that time.