REDOX PROCESSES IN DIAGENESIS OF SEDIMENTS IN THE NORTHWEST PACIFIC OCEAN

Abstract

Redox processes are quite widespread in bottom sediments of modern water bodies. Decomposition of organic matter in the mass of sediments, taking place as a result of microbiological and chemical processes, changes the physicochemical conditions, thereby bringing about a decrease in the redox potential of pore liquids. Under the reducing conditions created by the decomposition of organic material, the valencies, forms, and geochemical mobility of compounds of certain elements become changed. A possibility is thus created for the redistribution and concentration of certain elements in bottom sediment. Based on geochemical measurements in some 27 sediment cores collected from bottom sediments in the northwest section of the Pacific Ocean, information on the forms of iron, manganese, and sulfur, as well as organic carbon, is given. The sediments studied can be divided into three major categories: (1) reduced sediments of the continental slope; (2) transitional sediments of the marginal oceanic zone; and (3) pelagic sediments of the open ocean (red oozes). Apart from data on the areal distribution of the geochemical factors measured, profiles of element distribution versus depth of sediment core are given.