DOMES Site A, in the equatorial North Pacific, was surveyed in detail in an attempt to relate the distribution of nodules to sedimentation. The sea floor is characterized by a broad east-west-trending valley defined by strongly dissected highlands to the north and south. Sediment recovered from the highlands and from the north margin of the valley is late Quaternary. The associated nodules are small, often polynucleated, have smooth surface textures, and the dominant mineral is δ-MnO2. By contrast, cores along the south margin of the valley contain early Tertiary sediment; the nodules usually are large, discoidal in shape, all have a granular surface texture, and the dominant mineral is todorokite. Cores from the central part of the valley share properties with both of the above environments; the sediment is late Quaternary but the nodules are granular with dominant todorokite. The distribution of sediment and abundance of nodules is interpreted to be controlled primarily by the flow of Antarctic Bottom Water through the valley from west to east. The surface texture and mineralogy of the nodules, and possibly their chemical composition, may, in turn, be controlled by properties of the associated sediment.
