Sediment input and evolution of lacustrine deltas: The Breggia and Greggio rivers case study (Lake Como, Italy)

Two different sub-lacustrine deltas were recognised. In the south-eastern corner of the Breggia flood plain, a simple cone-shaped delta (minimum volume: 6.3×106 m3) develops in correspondence to the present Breggia mouth. About 600 m northward, a complex delta develops in front of the Greggio outlet. This is a composite sub-lacustrine body comprising a basal portion (minimum volume: 31.3×106 m3) interpreted as the Breggia paleo delta, and an overlapping smaller digitate sedimentary body (minimum volume: 0.7×106 m3) related to the present Greggio river. Depositional centres of the Breggia delta have changed through time, indicating a sudden migration of the river input in historical times, probably in the VI century AD.