Manganese and biotic debris associations in some deep-sea sediments.

Incipient manganese concretions occur in microcavities of planktonic skeletal debris (especially diatom frustules) in some Pacific Basin deep-sea sediments. These concretions contain over 50 percent manganese and very little iron (< 1 percent). There is a continuum of growth stages in the concretions having a diameter between 0 and approximately 2 millimeters, and a genetic relationship is suggested between the very small and the centimeter sized concretions.