Evolution and Plio-Pleistocene fault kinematics and basin infilling in the central Po Plain (Italy): an integrated analysis from subsurface data and analogue models analysis

The central Po Plain (Italy) is a complex geological system where the outermost fronts of two mountain belts, the Northern Apennines and the Southern Alps, coexist sharing the same foreland. Thanks to a dense dataset of seismic reflection profiles and wells (courtesy of Eni as part of the Ph.D project of Daniel Barrera, Univ. of Pavia) it has been possible to reconstruct in detail the buried structure of the Emilian arc, one of the three structural arcs that compose the outermost fronts of the Northern Apennines and the external fronts of the Southern Alps, buried in the central Po Plain. From these data, it is evident that the Emilian arc of the Northern Apennines is composed of three main thrust systems and related anticlines. It was also possible to reconstruct the geometry of the outermost fronts of the Southern Alps and, most importantly, the top of the Mesozoic carbonates, above which the main detachment levels of the Southern Alps have developed and whose geometry deeply influences the development of the Emilian Arc. The reconstruction of six regional Plio-Pleistocene unconformities of known age allows the restoration of some of the reconstructed tectonic structures, thus obtaining a slip value and the amount of slip rates along different tectonic structures and along the strike of the same structure.

Through these analyses, it is possible to argue on the Plio-Pleistocene kinematics of several tectonic structures in the central Po Plain, quantifying the recent tectonic activity of the main thrusts. The slip distribution and the along-strike deformation are rather inhomogeneous and do not follow the classic pattern of deformation propagation from the inner to the outer sectors of the chain but show evidence of inner thrusts reactivation and external thrusts with little or no activity in recent times. The possible causes of this rather complex kinematics have been investigated through a series of analogue models that, by reproducing the presence of structural highs and rheological inhomogeneities of the Po Plain, allow us to investigate if, and how much, some geological features affect the development of tectonic structures in time (kinematics) and space (along-strike variations).

The preliminary results of the research show how the buried structural highs in the Po Plain and the presence of the outer Southern Alps fronts modify both the structure's kinematics and the distribution of the along-strike deformation, creating the present-day complex structural framework.

This demonstrates the need for a 3D modeling approach and detailed quantitative reconstructions of deformation, not limited to the outer sectors of the Emilian arc, but considering the thrust system that constitutes the Northern Apennine as a whole.