A fundamental understanding of how sedimentary strata form requires distinction between deposition and accumulation of particles. Deposition refers to the temporary emplacement of particles on the seabed. Accumulation is the net sum of many episodes of sediment deposition and removal. The difference between rates of deposition and accumulation affects the ability of an environment to record sedimentary events. Radionuclide profiles of 234Th and 210Pb within the seabed can be used to determine 100-day deposition rates and 100-yr accumulation rates, respectively. On the continental shelf near the mouth of the Yangtze River, short-term deposition rates are about 4.4 cm/month, whereas accumulation rates integrated over a century are an order of magnitude less, about 5.4 cm/yr.