Neogene-Quaternary intraforeland transpression along a Mesozoic platform-basin margin: The Gargano fault system, Adria, Italy

Original field structural data and an offshore seismic reflection profile are here analyzed and compared with published earthquake and GPS data to constrain the tectonic evolution of the Gargano Fault Belt (GFB, Adria, Italy) whose kinematics has been contradictorily interpreted in the past. Field analyses show that the GFB consists of NW-striking to W-striking folds, thrusts, and left-lateral transpressional and strike-slip faults. The occurrence of a set of NW-striking solution cleavage supports the inference of an overall left-lateral kinematics for the GFB. Some synsedimentary structures indicate Miocene-Pliocene contractional and transpressional activity along the GFB, whereas strike-slip faults affecting some conglomerates dubiously dated back to Pleistocene times suggest a recent strike-slip activity. The seismic reflection data show that the offshore prolongation of the GFB consists in an anticline cut by high-angle faults arranged in a positive flower-like structure and grown mostly since Miocene times along a Mesozoic platform-basin margin. From the original and published data, at least three major tectonic phases can be inferred for the GFB: (1) a middle-late Miocene phase; (2) a middle-late Pliocene phase; and (3) a Quaternary phase including the recent and present seismic activity. All these phases are mainly characterized by contractional to left-lateral transpressional and strike-slip displacements. These displacements are consistent with the regional contractional tectonics occurred within the framework of Africa-Eurasia convergence. The estimated horizontal displacement for the GFB suggests that such deformation zone is not a first-order plate boundary across Adria unless this boundary is still incipient.