Internal growth features of manganese nodules from the Indian Ocean

Abstract

Two major structurally distinguishable growth zones are recognised in manganese nodules studied. The inner zone is characterized by widely spaced, isolate columns and abundant chaotically folded microlaminations. In the outer zone, chaotic folding of layers is absent, and the columns are well organised, compact cones sometimes grading to a vague colloform layering. Such fabric differences suggest a change in the environment from the inner to the outer zone of growth. Small-scale discordance features in different layers also indicate several minor interruptions during growth. Presence of rounded rock fragments (along with angular clastics) in nodules suggests the possibility of reworking of some clastics in regions of strong submarine topographic variations, without involving much lateral transport.