3D geological modeling of a portion of the high Val d’Agri (Southern Apennines, Italy)

This contribution deals with the three-dimensional reconstruction and kinematic analysis of a restricted area on the North-Eastern side of the high Agri Valley. This area lies in the inner portion of the Lucanian Apennine,where thrusts and related folds developed in Miocene-Pliocene time and deformed a highly heterogeneous sedimentary cover, consisting on Triassic-Tertiary sedimentary successions, which were deposited within pelagic basins and adjacent carbonate platforms. The modern morphologic-structural frame is the result of the subsequent late- and post-orogenic extensional tectonics that dissected the pre-existing contractional, thrust-dominated architecture. Low-angle extensional faults, active during the Pliocene- Pleistocene, were responsible for early tectonic exhumation and unroofing processes, mostly localised at the front of the Campania- Lucania Platform. Extension within the uppermost structural units is documented by the occurrence of highly discontinuous slivers of platform rocks belonging to the Campania-Lucania unit; these are bounded by gently dipping tectonic contacts, and sandwiched between pelagic deposits pertaining to the Ligurian and Lagonegro domains. Field investigation allowed to detail the relationships among post-orogenic structures in the study area: low-angle normal faults are truncated by a normal faults system, roughly N40 oriented; the latter subsequently superimposed by more recent sets of highangle normal faults, NW-SE oriented, that became the dominant structural features from Pleistocene time onwards, leading to the development of the Agri Valley basin. The digital modelling aimed to reconstruct the architecture of the superimposed fault systems and verify the geometrical consistency of the interpreted fault blocks, and the viability of the above described tectonic framework, as currently represented in the geological map. With this goal, an initial static model was constructed by using geo-referred field data, interpreted geological map and related cross-sections. Seriated cross-sections obtained from the initial model allowed refining the geological interpretation in three-dimensions, neglecting parasitic structures and tidying contacts in a geometrically viable and internally consistent model. This provides the base for the kinematic analysis by means of 3D restoration algorithms incorporated in MoveTM, the structural geology modelling software used for this study. As partial results of this ongoing research, we present a coherent model of the main high-angle faults architecture, and the predicted un-faulted geometry of the folded multilayer truncated by lowangle faults. The NW-SE striking normal faults have small strike-slip component. They offset steep N40-N35 oriented faults; both systems deform shallow dipping tectonic surfaces delimiting the top of the folded Mesozoic rocks.