Bioturbation nodules

Oxic Diagenesis Metals remobilized from sediments lying in the oxic zone. Remobilization likely occurs in anoxic microzones adjacent to nodules. Bioturbation is an important metal transport agent. Some nodules now found in oxic sediments were likely formed during times when the redox boundary was closer to the seafloor. 10-50 Todorokite (high Cu and Ni content) 32% 5-10 15-20... 

Three mechanisms have been proposed to explain how particulate metals could be transported within such sediments so as to support the growth of Fe-Mn nodules (1) anoxic microzones, (2) bioturbation, and (3) shifts in the depth of the redox boundary over time. Anoxic microzones are present within fecal pellets and the interiors of radiolarian shells where detrital POM is still present. Metals mobilized within these microzones should be able to diffuse through the sediments for substantial distances... 

The deep-sea radiolarian ooze is a biologically active zone as we could observe by the bioturbation of the sediments. Thus, the question arises how far the biologic processes can influence the growth of manganese nodules. 

For long timescales the fluctuations in °Be flux are damped out by bioturbation in slowly accumulating sediments or averaged out in very slowly growing manganese nodules and crusts as discussed below. 

Tidally influenced/estuarine facies association. Fine- to medium-grained sandstones with elay drapes interbedded with bioturbated siltstones and mudstones containing pyrite nodules. 

---