Structural evolution of the Bracciano volcano-tectonic depression, Sabatini Volcanic District, Italy

Abstract

Abstract The Latian volcanoes of Central Italy form several K-rich volcanic districts, some of which are characterized by large volcano-tectonic depressions filled with lakes. The development of these large depressions (>8 km in diameter) occurred from 0.4–0.3 Ma bp , during a climax of regional extension. Analysis of geophysical and deep drilling data and detailed field analysis, allows reconstruction of the evolution of the Bracciano volcanotectonic depression in the Sabatini Volcanic District, northwest of Rome. This depression developed during the Upper Pleistocene inside a NE-trending half-graben structure. The evolution of the half-graben has been driven by NE-trending regional faults which were reactivated during volcanism. Magma rose along these faults and came to rest at 4–7 km depth, probably as a laccolithic body, and was then erupted with emplacement of large volume ignimbrites. A lava plateau recognized by drilling data in the southern and western sectors of the depression is interpreted as being associated with NE-striking swarms of feeder dykes. The final downsagging was caused by NE and NW-trending regional faults after 0.17 Ma. The eastern depression morphology was modified by late Pleistocene N-trending strike-slip faults which were accompanied by intense hydromagmatic activity. Hydromagmatic craters are distinguished in the eastern margin of the area and in the southeastern part of Lake Bracciano in high-frequency seismic sections.