Structure and evolution of the Sacrofano-Baccano caldera, Sabatini volcanic complex, Rome

Abstract

Sacrofano eruptive center, in the eastern part of the Sabatini volcanic complex, was active between 0.5 and 0.09 m.y. ago. The Baccano geothermal area lies at the western edge of Sacrofano caldera. Sedimentary substrata that form the reservoir for this geothermal system were exposed at the surface at the beginning of volcanic activity. The volcanic history of the Sacrofano center can be divided into three stages: 1. (1) Construction of the Sacrofano pyroclastic edifice by predominantly Strombolian activity. 2. (2) Collapse of Sacrofano caldera following eruption of pyroclastic flows. 3. (3) Development of the Baccano explosive center at the western edge of Sacrofano caldera and collapse of Baccano caldera. Hydrovolcanic activity that began at the end of the first stage of Sacrofano can be explained by a drop in the magma level in the conduit that relieved hydrostatic pressure in the aquifer. As intense fracturing associated with caldera collapse penetrated the carbonate reservoir, the entrapped water flowed towards the conduit to balance the pressure change. The close link between tectonism and volcanism in the Sacrofano center suggests that eruptions there may have been triggered by gravity faults related to regional tectonics.