Long‐Term Tectono‐Stratigraphic Evolution of a Propagating Rift System, L’Aquila Intermontane Basin (Central Apennines)

Abstract

AbstractUnderstanding the long‐term tectono‐stratigraphic evolution of active extensional faulting is crucial for unraveling the mode through which continental rifting propagates in space and time. The Pliocene‐Quaternary L’Aquila Intermontane Basin (AIB) in central Apennines offers a natural laboratory for studying a propagating continental rift. Seismicity is related to NW‐SE‐striking normal faults that have been accommodating crustal stretching since the Late Pliocene. Through a multidisciplinary approach integrating field, mineralogical, geochemical (C‐O stable and clumped isotopes) and geochronological (40Ar/39Ar, U‐Th) analyses, this study focuses on the structural connection between the Mount Pettino Fault (MPF) and the Paganica Fault, two active, left‐stepped basin boundary faults of the AIB. A two‐stage tectono‐stratigraphic evolution is proposed during transition from localized to delocalized deformation and fault linkage. Stage‐1 (pre‐Middle Pleistocene) corresponds to nucleation and growth of the MPF, characterized by a ∼5 m thick exhumed fault core, consisting of an isotopically closed cataclasite (T (∆47) ∼33–50°C). Stage‐2 corresponds to the development of a distributed zone of NW‐SE and E‐W extensional faulting in the overlay zone with the Paganica Fault, which is interpreted as a transfer zone linking the basin boundary faults, with maximum long‐term slip rates comparable to those of the connected faults. Structurally controlled circulation of meteoric fluids promoted carbonate veining and travertine formation (T (∆47) ∼8°C). U‐Th carbonate dating of Stage‐2 mineralizations constrains the tectonic activity in the transfer zone at least at ∼182–331 ka. Implications on the tectono‐stratigraphic evolution and on the seismotectonic scenario of the AIB are discussed, providing geodynamic inference at regional scale.