Constraints on the interpretation of the CROP-04 seismic line derived from Plio-Pleistocene foredeep and thrust-sheet-top deposits (Southern Apennines, Italy)

• The structural architecture of the Southern Apennines is schematically described by a buried duplex system of shallow-water Mesozoic-Tertiary carbonates (Inner Apulia Platform of petroleum geologists) overlain by a thick pile of NE-verging rootless nappes. Nappe stacking took place mainly during Miocene times. Subsequently, in the early Pliocene, the entire pile of nappes was tectonically transported over the south-western margin of the Apulia Platform. During middle-late Pliocene and early Pleistocene times, finally, the portion of Apulia Platform presently represented in the buried duplex system underwent compressional deformation. The available seismic profiles do not allow an univocal interpretation of the Apennine deep structure, so that strong disagreements exist among geologists about the amount of internal shortening in the Apulia-carbonate duplex system and about the degree of involvement of the crystalline basement in the roots of the mountain chain. An argument used by the supporters of the thick-skin tectonic interpretation in order to discard thin-skin deformation is that the absence of an important basement involvement in the Southern Apennines would require unrealistic amounts of shortening. The present paper illustrates a series of geological features that prove a minimum shortening of about 90 kilometers within the Apulia carbonates during middle-late Pliocene and early Pleistocene times. Such an evidence obviously removes the principal bias against tectonic interpretations of the CROP-04 deep seismic profile implying thin-skin structural restorations.