Upper miocene shallow-water turbidites from western Tuscany

A sequence of graded ophiolitic sandstones, 120 m thick (Sanguigna Formation), outcrops within the Messinian Evaporite Group in a limited area near Gabbro, Fine Basin, western Tuscany.The formation lies between fine-grained sediments laid down under a thin water-cover. The graded beds show, on the other hand, many features typical of proximal turbidites, such as amalgamated layers, scour-and-fill structures, clay flakes and lumps, top-truncated Bouma sequences. Grain-size analyses suggest that they were deposited from high-density turbidity flows.The petrographic composition and the grain fabric indicate that the feeding was from the northeast across the Fine Basin. From the inferred dimensions and depth of the basin, the mean slope should have been less than 1°. The turbidity currents probably originated at a river mouth during flood stages.The Sanguigna graded beds are compared with occurrences of shallow-water turbidites.