From extension to contraction in syn-orogenic foredeep basins: the Contessa section, Umbria-Marche Apennines, Italy

Syn-orogenic deposits that occupy foredeep basins commonly experience contr action related to the migration of fold-and-thrust systems toward the forel and, This contraction may overprint the earlier extensional deformation tha t is related to the initiation of the basin. Although predicted by models f or foredeep development, evidence for extension predating contraction at di fferent scales is not extensively recorded in syn-orogenic deposits. Mesosc opic structures from the Contessa section, in the Umbria-Marche Apennines, Italy, reveal a complex history, characterized by extension soon before the contractional deformation. Normal faults predate the folds and thrusts tha t are related to the Miocene-age orogenic event responsible for the develop ment of the Apennines. Extensional deformation may have resulted from flexu ring of a lithospheric plate induced by the load of a stacking thrust pile. The transition from extension to contraction could play an important role in the evolution of belt-foredeep-foreland systems, as it could reflect the migration of advancing thrust fronts toward the foreland.