FERROMANGANESE NODULES OF THE KARA SEA

The intermittency of thin mainly manganese rich and iron rich layers o ccur in flat caky nodules of the Kara Sea. The manganese rich layers a re mainly composed to birnessite (buserite 1), the iron rich layers ar e composed of bacteria like particles of protoferrihydrite. Mineralogi cal, crystallochemical and chemical studies of these nodules showed th at they are shallow diagenetic ones. They may were formed during perio dically changed intensity of bottom circulation and varying conditions of accumulation and remove of sedimentary material.