Formation and persistence of extensional internally-drained basins: the case of the Fucino (Central Apennines of Italy)

The interaction between sedimentation/erosion and faulting represents one of the most intriguing topics in landscape and tectonics evolution. Recently, several studies attempted to unravel this issue but only few of them have been able to document the feedback between faulting and sedimentary loading. Here, we focus on how the sediment loading/unloading influences the dynamic of the faults system taking as study case the Fucino Basin in Central Apennines (Italy). The Fucino Basin represents a remarkable case study with respect to the other main extensional basins in the Apennines, because of its large dimension, rectangular shape, significant sediment thickness and more important, its endorheic nature throughout its evolution.

We present a detailed structural analysis all around the basin, investigating the kinematic and geometry of each main fault strand. The slickensides analysis reveals multiples families of slip-vectors and timing of activity which suggest a changing from N240° to N200° occurred during middle-Pleistocene. Moreover, using a simple isostatic model, we estimate that up to the 30% of the total geological displacement of the faults, which overall ranges from 0.5 to 3.5 km, is related to the sediments loading/unloading. Then, we demonstrate a positive feedback between sedimentation and faulting which may also lead to a re-organization in fault-kinematic related to a significant increasing in the vertical stress. Finally, we propose a conceptual model to support the permanent endorheic configuration of the Fucino basin, mainly related to a fault-slip increasing and kinematic changing due to the sediment loading.