Pop-up structure in massive carbonate-hosted fold-and-thrust belt. Insight from field mapping and 2D kinematic model in the central Apennines

Fold-and-thrust belts are characterized by the occurrence of foreland-verging thrusts and antithetic backthrust, which develop in the hangingwall of thrust sheets. Both thrust and backthrust bound the so-called pop-up structure, which is a deformed zone characterized by thrust- and backthrust-related anticlines. Pop-up structures mainly develop in fold-and-thrust belts characterized by a multilayered sedimentary sequence, consisting of limestones, marls, and shales, deformed above a weak décollement, such as evaporites. However, in this work, we combine field mapping, stratigraphic constrains, and structural analysis with 2D kinematic forward modeling to document a pop-up structure developed within limestones/dolostones, deformed above a strong décollement consisting of dolostones, in the central Apennines, Italy. In particular, we describe a SW-verging anticline and a NE-verging anticline in the SW and NE margin of the Serra Lunga ridge, respectively. Such folds were generated by a NE-dipping backthrust and by SW-dipping forethrust, respectively. Therefore, we suggest that the Serra Lunga ridge represents a pop-up structure, showing geometries similar to other pop-up structures observed within fold-and-thrust belts characterized by a multilayered sedimentary sequence. In addition, backlimb tilting of backthrust-related anticlines generates the forelandward-dipping monoclines, observed within thrust sheets in the Central Apennines and in several fold-and-thrust belts worldwide.