Reconstruction of continental margin architecture deformed by the contraction of the Lagonegro Basin, southern Apennines, Italy

Thrust propagation through previously rifted continental margins may result in fold and thrust belts whose structure is strongly controlled by the inherited basin architecture, as it occurs in southern Italy. The Lagonegro units of the southern Apennines comprise a deformed pelagic basin succession showing variable stratigraphic characteristics, mainly lateral variations in both facies and thickness, interpreted to be due to a complex basin topography related to a Triassic rifting event. In contrast to previous studies, cross-section balancing and restoration indicate that the Lagonegro units exposed in the high Agri Valley area suffered relatively limited internal shortening (8 km, i.e. 35%). Early deformation of these rocks, later incorporated into a large-displacement thrust sheet, was dominated by folding around (present-day) roughly north–south-trending axes. The attainment of a regional décollement level was favoured by an early mild inversion of the basin, producing a roughly similar structural elevation of both hanging-wall and footwall successions to Mesozoic faults. Most of the contractional deformation was accommodated by buckling of the Mesozoic syn-rift strata between synsedimentary faults, which represented major mechanical interfaces. Early strain localization in the Lagonegro Basin ahead of the active thrust front was most probably mechanically controlled by a faulted crustal segment which originally lay, within the continental margin, between two massive carbonate platforms.