Sedimentation rates and characteristics of manganese micronodules

Resumo

A study of core sections from the northern tropical Pacific (Northeast Basin) revealed that pelagic sediments are represented by Quaternary oxidized carbonate-free clayey‒radiolarian to radiolarian‒clayey mud, miopelagic clays locally enriched in radiolarians, and pre-Pleistocene miopelagic to eupelagic clays, zeolite‒clayey varieties, and zeolitites. The study also included an analysis of the grain-size and chemical composition, abundance, mass, and distribution of manganese micronodules (MN) contained in these sediments. The data made it possible to calculate relative sedimentation rates (Vr) in sections. In calculations, the estimate of the absolute (V) sedimentation rates for the upper (homogenous) core layer (approximately 5 ka old) was taken to represent a basic value. The values of relative sedimentation rates give grounds to assume that the mass of micronodules (Pmn), average mass of a single micronodule (Pmn/Nmn), mass of the sediment fraction (Pfr > 005 mm), and abundance of micronodules in sediments (Pmn/Psed) reflect the trends of variations in pelagic sedimentation rates.