Lithological Control on thrust-related deformation in the Sassa-Guardistallo Basin (Northern Apennines hinterland, Italy)

The Sassa-Guardistallo Basin (SGB) is located close to theTyrrhenian Sea and represents one of the most internalNeogene^Quaternary hinterland basins of theNorthern Apennines fold-and-thrust belt. Its sedimentary succession consists of ca. 400-m-thick LateTortonian^Messinian continental ^ largely conglomeratic ^ units overstepping a mainly shaly substratum(Palombini Shales) and overlain by LateMessinian evaporites and marine to continental Pliocene^Pleistocene sediments.This stratigraphic succession can be approximated to a composite rheological multilayer that dictated the style of basin deformation.Detailed geological mapping and structural analysis revealed that basin deposits were a¡ected by compressional deformations that can be found both at map and outcrop scales.Decametric splay thrusts emanating from the substratum^conglomerate interface locally double the continental succession and are bounded by a roof thrust along the LateMessinian evaporite de¤ collement, de¢ning a deformation pattern consistent with a duplex-like structure.The time^space structural evolution of the basin inferred from the ¢eldworkwas addressed and tested by analogue modelling that approximated the rheological strati¢cation of the study area to a layered brittle^ductile system.The model results support the hypothesis that the evolution of the thrust systema¡ecting the SGBstarted as an early £oor imbricate fan thrust systemthat successively evolved to a duplex structure as the link thrusts propagated into the upper de¤ collement layer that resulted from the deposition of the LateMessinian evaporites.Models display many structural features that may be comparedwith the natural prototype, and highlight the importance of syntectonic sedimentation in the development and evolution of tectonic structures.The results of this study retain relevant implications for theNeogene evolution of theTyrrhenian Basin^Northern Apennines system.This study also supports that combining between ¢eld structural analyses and analogue modelling can give useful hints into the evolutionary history of tectonically complex areas.