Quantitative evaluation of bioturbation rates in deep ocean sediments. 2. Comparison of rates determined by super(210)Pb and super(239,240)Pu

Excess super(210)Pb was determined in six abyssal cores from the Eastern Atlantic, Hatteras Abyssal Plain, and Puerto Rico Trench. A bioturbation rate for each core was evaluated using the mixing model of Guinasso and Schink. The rates were compared to mixing rates evaluated for the same cores using super(239,240)Pu. In all cases, the excess super(210Pb-derived mixing rates were lower than the plutonium-derived mixing rate. ) super(2)39,240u) was also present at greater depths than excess super(210)Pb. One possible explanation for these observations is the association of plutonium with particles of greater food value which are bioturbated at faster rates.