Plio-Pleistocene foraminiferal assemblages of the Monte Mario site (Rome, Italy)

Tunnel construction at Monte Mario hill (Rome) facilitated detailed study of the Monte Mario historical succession. Qualitative and quantitative analyses were performed on foraminiferal assemblages in order to define new stratigraphical and palaeoecological constraints for this historical site. From a chronostratigraphic point of view, micropalaeontological data assign the basal part of the succession (Monte Vatican Formation) to the Early Pliocene (Zanclean Stage, upper part of Globorotalia puncticulata Zone) based on the presence of the marker species Globorotalia puncticulata. The presence of Dentoglobigerina altispira altispira, a well-known indicator of the upper Zanclean Stage in the Latium area, confirms the age assignment in agreement with nannoplankton data. The upper part of the Monte Mario Formation is attributed entirely to the Earls' Pleistocene (Calabrian - Santernian substage) based on the presence of Bulimina etnea Palaeoecological reconstructions are based on quantitative proxies (percentages of single taxa, inbenthic and oxyphilic species, diversity indices, %P [(P/P+B)%]) that were used to evaluate important palaeoenvironmental and palaeoclimatic conditions. Pliocene deposits (Monte Vatican Formation) record an upper bathyal environment characterised by warm oligotrophic water and well-oxygenated bottom water Pleistocene sediments (Monte Mario Formation) record highly variable environments controlled by sea level oscillations caused by the combined effects of tectonics and climate change. The deepest environments are recorded in the Pleistocene Farneto silts and represent an upper circalittoral environments that are characterised by cold water with enriched organic matter content and nearly eutrophic conditions. A more oxygenated, shallow-water environment with widespread vegetated cover is recorded from the Grey sands with Arctica islandica Member to the basal part of the Yellow sands with "panchina" Member More marginal environments developed successively as a result of a shallowing trend. Lagoon/brackish lagoon environments characterised by oligospecific euryhaline foraminiferal assemblages develop to the Yellow sands with silty intercalations Member The last member Clays and Cerastoderma-bearing sands, is characterised by the re-establishment of of normal marine infralittoral conditions of nutrient input and fresh-water influence. The succession ends with a more confined brackish lagoon environment, which relates to the progradational step of the uppermost portion of the Monte Mario Formation.