The Laga Detachment Zone in the M. Marine Anticline

Detailed mapping integrated with sedimentological and structural observations has allowed to elucidate the tectono-sedimentary evolution of the inner margin of the Laga Foredeep. The latter originated in front of the junction between the Umbro-Marchean and Lazio-Abruzzi segments of the evolving fold-and-thrust belt of the Apennines. The Laga Fm of Late Miocene age represents the main stage of turbiditic foredeep activity. Towards the end of the Early Pliocene, the inner margin of the Laga Foredeep was overridden by the M. Giano-M. Gabbia Unit of the Lazio-Abruzzi Apennines. In front of this, a flat developed in the marly series separating the Laga Fm from the underlying essentially Mesozoic carbonate section. The Laga Fm experienced a significant forward translation over the Laga Detachment Zone. Subsequently, the rootless M. Marine Anticline and several more external structures evolved in the substratum of the Laga Basin. Hereby, the Laga Detachment Zone was deformed passively as an upper flat. Gravitational forward gliding of the Laga Fm over the Laga Detachment Zone affected the steepening forelimb of the M. Marine Anticline. Finally, as orogenic compression ceased, the backlimb of the M. Marine Anticline was downfaulted in consequence of ramp collapse.