The coarse-grained fluvial deposits of the Plio-Pleistocene Valdarno intermontane basin consist of massive or cross-stratified coarse gravel grading upward into cross-laminated sand overlain by massive overbank silt and clay with widespread pseudogley pedogenesis. The overall characteristics of such deposits (fining upward, abundance of overbank sediments, occurrence of extensive planar cross-stratification) would suggest deposition by a coarse-grained meandering river.

A detailed analysis of the relation between the depositional surface and the fabric of pebbles in planar crossbeds indicates downstream rather than lateral accretion. In fact, the dip of the intermediate axis of the pebbles parallels the foreset dip. Such a...