Geology of the Variscan basement of the Laconi-Asuni area (central Sardinia, Italy): the core of a regional antiform refolding a tectonic nappe stack

Abstract

The study area extends in central Sardinia between the coordinates 8°56′00″/39°55′00″ (NW corner) and 9°03′00″/39°50′00″ (SE corner). It forms part of the Sardinian Variscides that are characterized here by the western-most aspect of a regional structure known as the Flumendosa Antiform, which runs ENE-trending for more than 50 km along its axis. It represents the envelopment of several, upright km-scale minor folds that refold the different tectonic units of the Variscan Nappe zone characterized by a number of isoclinal folds, with axial plane foliation and thick ductile shear zones. The antiform is in turn deformed by late-orogenic extensional structures, namely asymmetric folds and narrow, low angle ductile shear zones that generally reactivate earlier collisional structures.The 1:12,500 scale map completes the mapping of this important regional structure, meaning that a detailed survey of the entire mega-structure is now available. This enables more detailed structural analyses of poly-deformed areas in low-grade metamorphic conditions to be conducted, given the robust knowledge available of the lithostratigraphic succession and the geometric and kinematic outlines.