Geometria e cinematica delle anticlinali dell'Appennino centrale esterno: Il ruolo delle faglie dirette giurassiche

The outer zones of the Central Apennines are characterized by arcuate thrusts and related NE-verging folds that affect a ca. 2000 m thick Mesozoic-Neogene sedimentary succession. The base of the succession is represented by a massive 800 m thick platform carbonate unit of Early Liassic age (Calcare Massiccio Fm.), that grades upwards into well-bedded pelagic carbonates, marls and siliciclastics. The Jurassic portion of the succession displays thickness and facies variations, that are controlled by synsedimentary normal faults: these dismembered the Early Liassic carbonate platform into differently subsiding seamounts and troughs. The onset of Neogene orogenic deformation was responsible for the contraction of the sedimentary succession. Detailed analysys of some anticlines reveals the occurrence of high-angle thrusts within the Calcare Massiccio Fm., whose displacements are accommodated by folding within the overlying pelagic succession. Thrust-related folding was locally influenced by the occurrence of Jurassic normal faults that, where present, inhibited thrust propagation toward the foreland. Folding at the expenses of Jurassic normal faults therefore results in structures that differ significantly in geometry and kinematics from those developed across a layer-cake stratigraphie template.