Turbidite Depositional Systems and Architectures, Cilento, Italy"

Analysis of the extensive Miocene siliciclastic outcrops in Cilento, southern Apennines, allowed the identification of four turbidite depositional systems. The basal unit is a sandy silt-rich turbidite system that is present in the entire area. It consists of thin-bedded turbidites in sheet lobes. Debris-flow deposits truncate this system and mark the start of the second system. It is an atypical sand-rich system that developed differently in different areas of Cilento. In the west, the turbidites are conglomerates and massive sandstones that represent a progradation from sandy lobes to channels. In the east, thick, amalgamated packages of coarsegrained sandstones and conglomerates, typical of confined erosional channels, are present. In both areas, finer grained, thinner beds with intercalations of a few coarse-grained, chaotic beds characterize the upper part of this second system. The overlying third system, a sheet system, consists of alternating mudstones and sandstones with a significant calcareous component and some beds that are decimeters (>50 ft) thick. These deposits extend laterally for tens of kilometers (>20 mi), sometimes abruptly decreasing in thickness to the east. The intercalated, chaotic megabeds are evident in this eastern area only. The fourth system, a sandy/gravelly system, is present only in the east and is developed with an angular erosion surface. It consists of amalgamated massive sandstones and conglomerates, which may be ascribed to wide, low-sinuosity channels and their terraces along a steep, structurally confined slope. It is possible to determine the paleotopography of the basin based on the architectures of the approximately 2000-m- (6560-ft)-thick interval. These differences, which are also evident in petrographic data, are attributed to structural highs that developed because of deformation of the substratum. Basement segmentation and paleohighs controlled the development of the second depositional system. Starting near the top of the second system and throughout the third, the highs were less important in confining and ponding the turbidite flows. Environmental conditions then changed after the deposition of the uppermost chaotic megabed on which the fourth system lies. The boundaries of each of these four systems coincide with the boundaries of lithostratigraphic units as defined by Nardi et al. (2003) and Cammarosano et al. (2004). Keywords: turbidite depositional systems, facies architecture, basin topography, Cilento Flysch Basin, Southern Apennines.