Iron–manganese banding in Oneida Lake ferromanganese nodules

Abstract

Ferromanganese nodules in the deep-sea and in freshwater lakes usually accrete layers rich in manganese oxides alternating with layers rich in iron oxides¹. The mechanism producing these alternating layers is unknown; indeed, the mechanism producing the nodules themselves is unknown. In Oneida Lake, a large freshwater lake near Syracuse, New York, precipitants from the lake water and the surfaces of nodules at the sediment–water interface are enriched in Mn, whereas nodules buried in lake sediments have surface layers enriched in Fe. It is hypothesized here, using field and laboratory evidence, that reduction and mobilization of Mn from the nodule surface during periods of anoxic sediment cover produce the high Fe layers observed in the nodules.