Deep-Water Volcaniclastic Layers in the Late Messinian Apennines Foreland Basin Unravel the First Calc-Alkaline Rhyolitic Eruption in the Central Italy Magmatic System

A package of upper Messinian volcaniclastic layers (UMVLs), exposed in the deep-water foreland basin system of the central Apennines (Italy), is the volcanic product of a rhyolitic eruption dated to 5.5 Ma. These UMVLs are an important marker for stratigraphic correlations along the central Apennines foreland basin system, but their source is still debated and poorly understood. Italian Plio-Quaternary volcanism exhibits significant petrological and geochemical variability, causing debate over magma genesis and differentiation. Investigating the magmatic evolution of central Italy is crucial for understanding one of the most complex geodynamic settings on Earth. The first evidence of efficient magma differentiation, producing eruptible calc-alkaline rhyolitic magmas, is the San Vincenzo eruption at 4.41 Ma. Our sedimentological and petrological analyses of UMVL exposures indicate a possible volcanic source in the northeastern Tuscany Magmatic Province. This discovery implies a developed transcrustal magma reservoir system and suggests that efficient magma differentiation capable of producing eruptible calc-alkaline rhyolitic magma occurred about one million years earlier than the San Vincenzo eruption, marking these UMVLs as the first rhyolitic eruption associated with Italian Plio-Quaternary volcanism.