A case of manganese precipitate in the Taviharju esker, Kuusamo, North East Finland

Abstract

A manganese-iron precipitate of an exceptional size has been found in the Taviharju esker in Kuusamo, North-East Finland. The different forms in which manganese is known to be deposited in humid areas such as Finland are listed. The Taviharju case represents an example of cementation in gravel and coarse sand. The mechanism operates in the following way: Manganese and iron have been dissolved in reduced form, probably as complex organic compounds, in percolating ground water. When the water enters coarse esker material where oxidizing conditions prevail, the manganese, iron and dissolved organic compounds are oxidized and precipitated as electrically charged gels. These coat the mineral grains and cement them together to form horizontal layers rich in manganese. The soil may be termed gleyed.