The extent of racemization of isoleucine and aspartic acid has been measured on cetacean ear bones from the center of 8 manganese nodules in order to estimate the ages of the nuclei of the nodules and the rates of accretion of ferromanganese oxide layers. Age estimates obtained range from about 0.4 to 6 m.y., and rates of growth from <1 to about 10 mm/m.y. These rates are consistent with those obtained by other nucleus dating methods (K-Ar and fission track) and by layer dating methods (230Th, 231Pd, 10Be and 26Al)
