Type of Carbonate Production, Sedimentary and Tectonic Evolution of the Pliocene Mixed Carbonate Siliciclastic Unit (Macco) in the Tarquinia Basin, Central Italy

The Pliocene Epoch in the Mediterranean region marks the re-establishment of open marine conditions following the Messinian Salinity Crisis and the onset of modern Mediterranean ecosystems and climate. This study investigates the ‘Macco’ lithostratigraphic unit exposed in the Tarquinia area (northern Latium, Central Italy), a mixed carbonate-siliciclastic succession deposited along the passive margin of the Tyrrhenian back-arc basin during the Piacenzian. Integrated facies, stratigraphic, structural and morphostructural analyses reveal syn-sedimentary growth structures associated with segmented, first-order NW-striking faults up to 3–4 km long that strike NW-SE and generate accommodation space. Second-order NE-striking faults, which are up to 0.5 km long, played a key role in controlling the lateral distribution of lithofacies and the development of localised growth structures. The ‘Macco’ unit records deposition on a distally steepened carbonate ramp, characterised by coralline algae and larger benthic foraminifera in the middle ramp, and significant carbonate-siliciclastic mixing in inner and outer ramp settings. Three clino-stratified wedges reflect a complex tectono-stratigraphic framework. Nonetheless, the correlation with global eustatic curves suggests that the interplay between regional tectonics and eustatic sea-level fluctuations was the primary control on sedimentary architecture during the Piacenzian.