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

Understanding 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. Plain Language Summary: We studied how crustal stretching has been accommodated in the Apennine Mountains of central Italy during the Middle‐Late Pleistocene. By studying the L'Aquila Intermontane Basin, a Late Pliocene‐Quaternary sedimentary basin bounded by extensional faults, we investigated how the basin boundary faults evolve and connect over time. Using a variety of methods including fieldwork, mineralogical, geochemical and geochronological analyses, we focused on the overlapping zone between the Mount Pettino and the Paganica active extensional faults. We found that the Mount Pettino Fault experienced a two stage evolution, with the first stage involving the growth of the fault zone at depth, followed by exhumation and connection with the Paganica Fault. Fault linkage was associated with formation of diffuse carbonate veining and travertine deposition during the ∼182–331 ka time lapse. Such tectonic interaction contributed to reshape the basin architecture, transforming it from two separated, internally drained sub‐basins into a single, interconnected basin with external drainage. Results contribute to refine our understanding of how active extensional faulting nucleated, developed and interacted in space and time in the central Apennines. Key Points: En‐echelon seismogenic faults in L'Aquila Basin exhibit polyphase tectonic activity with stages of nucleation, localization and interactionTransition from soft‐ to hard‐linkage controlled basin evolution and Middle‐Upper Pleistocene sedimentationTectonic interplay among the various seismogenic faults regulate the seismotectonic setting of the region [ABSTRACT FROM AUTHOR]