GEOMETRY AND KINEMATICS FROM A WSW–TRENDING DEXTRAL TRANSFER ZONE: THE TRE MONTI FAULT (CENTRAL APENNINES)

The Central Apennines are characterized by a direction of maximum stretching oriented NE-SW. Despite this extension is mostly accommodated by normal slip on NW-trending fault segments, several faults have different orientation. In this study we present a detailed structural and geological survey to define the kinematics and architecture of an exhumed fault zone in Mesozoic carbonates, the WSW–trending and 8 km long Tre Monti–Celano fault zone, both by field and remote sensed methods (e.g. satellite pictures, aerial images, digital earth model). The Tre Monti–Celano fault zone is the northern boundary of the Fucino Basin, an intramontane half-graben filled by Plio–Quaternary alluvial and lacustrine deposits located in the central part of the Apennines chain, which was formed in Upper Pliocene and in Quaternary time by the extensional tectonic activity. The main fault plane consists of SSE-dipping normal fault cutting lower to middle Cretaceous limestone in the footwall and upper Pliocene to middle Pleistocene lacustrine deposits and subaerial slope debris in the hangingwall. Kinematics indicators, fracture orientation, and geometry of fault splays along the fault zone recorded mainly dextral transtension movement. The main fault is splitted into smaller segments (from 700 m up to 2 km in length) arranged with dextral en-echelon geometry. Inversion of kinematics indicators on fault segments oriented respectively ENE-WSW, NE-SW and NNE-SSW indicate a direction of maximum extension oriented NE-SW, accordingly to the direction of the maximum regional extension. These data suggest that the Tre Monti fault zone acted as a dextral transfer zone between two left-stepping major normal faults, oriented NW–SE and characterized by normal or slightly dextral oblique slip: the Venere-Serrone Fault in the south-east and the Velino fault in the north-west. Detailed mapping along the fault zone allowed to recognize different types of fault rocks generated by different lithologies involved in deformation and different amount of fault displacements. Further work will focus on a microstructural-mineralogical and geochemical characterization of natural fault rock samples to understand the mechanism of deformation and the role of fluid within these processes.