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An integrated approach to the study of the Central Apennines thrust system has been conducted, combining together new field, geophysical, organic matter maturity and mineralogical datasets. The area comprises one of the most studied basins of the Central Apennines: the Laga basin. It developed during the Messinian time and represents the link between the internal, uplifted, Lower Miocene fold-and-thrust belt to the west, and the external, more recent part of the chain, buried below a thick pile of synorogenic, Plio-Pleistocene clastic deposits of the Periadriatic basin to the east. The Laga basin is filled by several turbiditic sedimentary sequences, largely studied in the past and mostly included into the Laga Formation, classically considered the fill of a deep marine foredeep basin connected to the flexure of the subducted Adriatic lithosphere under the Apennines. Our results clearly suggest that during Messinian, the main factor controlling depositional system architectures was thrusts activity, which governed the localization of the main depocenter in the basin and its eastward space-time migration. The occurrence of thrust activity during deposition of most of the Laga basin sedimentary succession suggests that it can be described as an internally deformed but not migrating sedimentary wedge, having features recording the transition from foredeep to wedge top depozone.

The possibility of inferring paleoflow conditions of the Messinian turbidites from the Laga Formation (Central Apennines, Italy) is here analyzed by solving an inverse problem. This inverse problem is solved for elucidating the condition for flow ignition for current velocity, height, and sediment concentration by comparing field data with an analytical solution for the change in bed elevation, related to net-depositional turbidity currents. The obtained layer-averaged values are 2-5 m/s for current velocities, 40-100 m for current thicknesses, and 0.1-2% for sediment volume concentrations. Moreover, the duration time of these flows has been also estimated. Results show values from 1 to 15 hours, depending on the energy of the turbidity currents. This variability in the hydrodynamic conditions also provides some insight into the high-order cyclicity observed into the Laga turbidite deposits. A brief discussion on the vertical structure of a net depositional turbidity current is finally presented. The hydrodynamic conditions of a three-layer turbidity current are inferred from classical tank experiments. The behavior of each layer during the net-depositional phase of a realistic turbidity current is consequently described by using layer-averaged results of the inverse problem, as a function of the Richardson number and the Reynolds number. Results confirm subcritical turbulent behavior of the thin basal layer, a middle layer with a reduced turbulence, and an upper layer with a turbulent cloud where the mean kinetic energy is smaller than the turbulent kinetic energy.

This work investigates the physical stratigraphy and the sedimentological characters of the Messinian turbidites of the Laga Formation, central Apennines. In particular, the study concerns the lower Messinian portion of the Laga siliciclastic turbidites cropping out between the Mts. Sibillini and the Montagna dei Fiori-Montagnone anticline. The turbidite succession of the Laga basin was subdivided into three main allounits, Laga 1, Laga 2, and Laga 3, bounded by three unconformities and their correlative conformity surfaces, named I1, I2, and I3. Each of the three units show a fining and thinning-upward trend and they are stacked to form a succession with a clear forestepping pattern, reflecting the eastward migration of the basin depocentre induced by the Apennine thrust propagation. The sequence-stratigraphic interpretation of these deposits has allowed the three units to be framed in terms of 3rd- and 4th-order depositional sequences. Two 3rd-order sequences, namely Laga Depositional Sequence (LDS; uppermost upper Tortonian-lowerMessinian) and Cellino Depositional Sequence (CDS; upper Messinian- lower Pliocene), were recognized. The evolution of both the sequences was controlled by tectonic activity and climatic changes, and records an increased thrust activity followed by a slowdown of thrust motion and by a subsequent re-acceleration of the process. This work describes, in particular, the depositional and stratigraphic features of the LDS, which constitutes a thick turbidite complex where the main architectural elements of a fan can be recognized: from slope to basin floor passing through a channelized sector. Two main processes were considered as responsible for the generation of the turbidite flows: fluvial floods and submarine failures of variable volume. Both these processes were closely related to development of shelf margin deltas migrating basinward and landward, in connection to relative sea-level fluctuations forced by a variable combination of tectonics and climate changes.