Constraints on the interpretation of the CROP-04 seismic line derived from the Late Pliocene to Pleistocene thrust-sheet-top and foredeep deposits

The Pliocene and Pleistocene deposits unconformably covering the allochthonous sheets in the Southern Apennine mountain chain and disconformably overlying the autochthonous Apulia carbonates in the Bradano Trough display remarkable stratigraphic signatures closely controlled by the trajectories of the active thrusts. Thrust propagation during the Pliocene and Pleistocene followed in the study area a quite simple leitmotif that recalls the advancing mode of a caterpillar, every stage of forward nappe displacement having been preceded and followed by a telescopic shortening of the structural edifice behind the inactive front of the tectonic wedge. This behaviour allows the recognition of well-defined tectonic cycles, each cycle starting with the activation of a long thrust flat and ending with a forward propagation of the active thrusts and the incorporation of new horses into the duplex system. Tectonic cycles have been recorded in the foredeep basin and on top of the allochthonous sheets by thrust-related depositional sequences, every sequence being divided into four systems tracts representative of the principal steps that describe the caterpillar-like motion of the tectonic wedge: 1)forward transport of the Apenninic nappes on top of a long thrust flat; 2)development of a steep ramp at the front of the tectonic wedge; 3)deactivation of the leading edge of the duplex system and out-of-sequence migration of the active thrusts towards the axis of the mountain chain; 4) forward migration of the active thrusts beneath and beyond the previously abandoned leading edge. We carefully analysed the different systems tracts of the Ofanto and Bradano depositional sequences along the CROP-04 transect in order to provide additional information about the relationships between thrust propagation and sedimentation in late Pliocene and early Pleistocene times. In this paper, new constraints about the kinematic evolution of the thrust belt-foredeep system in the 3.70 - 0.60 Ma interval will be presented. The new data have allowed us a quite accurate age determination of the growth of the principal tectonic structures both in the buried Apulia carbonates (e.g. San Gregorio Magno antiform) and in the roof units of the Apennine duplex system (e.g. San Fele antiformal stack and Ofanto synform).