Strike-slip faulting and block rotation: a possible triggering mechanism for lava flows in the Alban Hills?

Abstract

It is suggested in this paper that two distinct tectonic triggers, tapping different depths of a magma reservoir, may be the cause of nearly contemporaneous eruptions of lava flows and ignimbrites in the Alban Hills. The area between the Alban Hills and Rome underwent alternating regional extensional and strike-slip faulting during the Middle Pleistocene. The geometries of the main structural dislocations in Quaternary strata, combined with a statistical analysis of drainage network trends, show a structural pattern that is consistent with local strain partitioning in transpressive zones at strike-slip fault bends, superimposed on regional extension. Based on this analysis, it is suggested that local clockwise block rotation between parallel N–S strike-slip faults might have generated local crustal decompression, allowing relatively volatile-free magma to rise from deep reservoirs beneath the Alban Hills, triggering peripheral fissure lava flows. In contrast, the main ignimbrite eruptions appear to tap shallow, volatile-rich magma reservoirs and are controlled by extensional processes.