Tectono-Stratigraphic Evolution of a propagating extensional fault network: Insights from the L’Aquila Intermontane Basin, Central Apennines

Understanding the long-term tectono-stratigraphic evolution of active extensional faulting is key to deciphering how continental rifting propagates over time and space. The Pliocene-Quaternary L’Aquila Intermontane Basin (AIB) in the central Apennines serves as an ideal natural laboratory for investigating this process. Seismicity in the AIB is linked to NW-SE striking normal faults that have accommodated crustal stretching since the Late Pliocene. This study integrates fieldwork, mineralogical, geochemical (C-O stable and clumped isotopes), and geochronological (⁴⁰Ar/³⁹Ar, U-Th) analyses to explore the structural connection between the Mount Pettino Fault (MPF) and the Paganica Fault, two active, left-stepping basin boundary faults. The research proposes a two-stage tectono-stratigraphic evolution reflecting a shift from localized to distributed deformation and fault linkage. Stage-1 (pre-Middle Pleistocene) marks the nucleation and growth of the MPF, characterized by a ∼5 m thick fault core of isotopically closed cataclasite (T (∆47) ∼33–50°C). Stage-2 involves the development of a distributed fault zone linking the MPF and the Paganica Fault via a transfer zone. This zone facilitated meteoric fluid circulation, carbonate veining, and travertine formation (T (∆47) ∼8°C). U-Th dating of Stage-2 mineralizations constrains tectonic activity in the transfer zone to ∼182–331 ka. These findings provide insights into the tectono-stratigraphic evolution of the AIB and its seismotectonic behaviour, with implications on the regional geodynamic reconstructions.