The use of 7Be to identify event and seasonal sedimentation near the Po River delta, Adriatic Sea

In October 2000, a major flood event of the Po River occurred. The resulting seabed deposit was initially sampled in December 2000, and most sites were reoccupied on subsequent cruises over a 3-yr period. Using the maximum penetration depth of the short-lived radioisotope 7Be (half-life 53.3 d), the flood deposit was found to be up to 15 cm thick. Individual depocenters of thick strata were located immediately adjacent to the distributaries at the river mouth in relatively shallow water (< 30 m). These flood deposit thicknesses are minimum estimates because the depth of 234Th (half-life 24.1 d) exceeds that of 7Be in physically stratified flood sediment, indicating that the first sediment deposited during the flood event likely originated from the river channel. 30–55% of the estimated sediment load delivered to the shelf during the flood event can be accounted for using 7Be penetration depths. Seasonal deposition also can be quantified using 7Be, after removing the effects of biological mixing. Seasonal deposition rates are a maximum of 6 cm yr− 1 near the Pila distributary, decreasing to 2 cm yr− 1 in the southern portions of the dispersal system.