96 NEW YORK STATE MUSEUM 



Genesis of the Manganese Deposits 



The western foothill county of the Taconic range, in which the 

 bog manganese occurs, consists for the most part of irregular hills 

 more or less conical in shape and of no great height. The depressions 

 now occupied by the manganese bogs are no doubt a product of 

 preglacial subaerial and glacial erosion; the claylike materials filling 

 them are of glacio-lacustrine deposition. Since the withdrawal of 

 the glacier, this region has been reclaimed by vegetation giving rise 

 in some of the depressions to peat. 



Trenchings, test pits and drillings frequently made throughout the 

 bog area all testify to a recent origin for the manganese. The lower- 

 most underlying materials as a rule consist of a bedrock of grit or 

 schist, overlaid by consolidated hardpan or till with or without a 

 manganiferous cement and a bluish or light gray' clay, containing 

 manganiferous nodular aggregates or nodular wad, surfaced with a 

 clayey loam or a dark loam clay with nodular bog manganese. 



The immediately associated beds of bluish or light gray clay 

 holding faceted boulders and rock fragments, are of glacial origin, 

 arising from fluviatile or lacustrine deposition. Later additions were 

 made in the form of sand, iron and manganese, constituting the 

 clayey loam soil and the bog manganese and bog iron ore. The 

 nodular form assumed by the oxide of manganese, as shown by 

 Hjort and Murray in connection with deep sea nodules and by the 

 writer in the study of Cambrian manganese of Conception and 

 Trinity bay, Newfoundland, is a phenomenon due to chemical and 

 physical causes, as will ' be discussed later in this paper. This 

 characteristic form, so far as revealed in Columbia county bogs, is 

 purely secondary, and the formation of nodules and nodular aggre- 

 gates is taking place pari passu with the addition of the oxides of 

 manganese. The fact that manganiferous waters have been and 

 are percolating through the clayey beds is most strikingly .brought 

 out by the coatings of Mn0 2 in the loose rock fragments and boulders 

 in the clay. 



The adjacency of the manganese deposits to the bogs and bog 

 waters' is a most significant relationship, so far as the immediate 

 genesis of the manganese is concerned. Chemical investigation leads 

 to the conclusion that manganese exists in surface waters either in 

 the form of the bicarbonate or the sulphate. Through oxidation 

 of either of. these, manganese is precipitated as the dioxide of man- 

 ganese. This oxidation may take place wherever oxygenated con- 

 ditions are present, such as at the surface of bog waters or in the 



