Characteristics of manganese micronodules as indicators of sedimentation conditions in pelagic sediments

Resumo

Pelagic sediments from three cores in the northern tropical Pacific zone (the northeast basin) have been analyzed for particle size and composition, as well as for number, mass and the distribution of protosyngenetic authigenic manganese micronodules (MN) in them. The sequences are represented by Quaternary carbonate-free clayey–radiolarian, radiolarian–clayey oozes, miopelagic clays, sometimes enriched in radiolarians, pre-Pleistocene miopelagic and eupelagic clays, zeolite–clayey sediments, and zeolitites. Based on factual data (volume of wet sediment, weight of dry sediment and micronodules, their number and proportions of four fractions, the contribution of MN in sediment, and others), the values of different parameters were calculated. The obtained parameters are statistically similar, which allowed us to reveal background and anomalous horizons of sediments and to assume their sedimentation conditions. Similar values of Р_MN/N_MN, Р_fr > 0.05 mm, Р_MN/Р_sed and the mass of micronodules suggest that precisely these parameters reflect the main variations in conditions of pelagic sedimentation.