446 DALE— CAMBRIAN MANGANESE DEPOSITS OF [April 25, 



tion resulting in a contemporaneous formation of manganese, cal- 

 cium and magnesium carbonate. As the analyses show from 1.25 

 to 32.92 per cent, of CaCOg and from .01 to 5.01 per cent, of 

 MgCOg this would seem to support such an action. 



There is a possibility that the decomposing organic matter 

 present in the muds might have caused a deoxidation of the sul- 

 phates of the sea-water and of MnO, with the subsequent formation 

 of FeSa and MnSa- The latter, being very unstable, would pass 

 immediately into the bicarbonate to be subsequently freed of its 

 CO2 to form the carbonate and if oxidized would pass into the 

 dioxide. Such a process might account for the carbonates and 

 oxides of manganese and the little pyrite that occurs. Though 

 there is evidence of life in the manganese deposits of Newfound- 

 land as furnished by the fossil trilobites, pteropods and phosphatic 

 accumulations, we have no evidence that there was any great abun- 

 dance. However these deposits resemble the Blue Muds studied 

 by Dittmar (6: 43) which are a variety of terriginous deposit which 



" covers about 15,000,000 square miles of the sea bed, and is chiefly found in 

 estuaries, harbours, enclosed seas, and along continental coasts where rivers 

 pour their detrital matter into the ocean." 



According to the " Challenger researches " there is an abundant 

 fauna on these muds, which feeds chiefly on the organic remains 

 that fall from surface waters. If any analogy can be made between 

 the ancient terriginous deposits and the more modern ones such a 

 chemical action as described above might very well have taken 

 place. 



If the muds on the bottom of the basin contained considerable 

 quantities of decomposing organic matter, conditions would favor 

 a reduction of the higher oxides of manganese, the evolution of 

 much CO2 and the consequent formation of the bicarbonate of 

 manganese. The subsequent liberation of the excess CO, from the 

 bicarbonate to form the carbonate and, where oxidizing influences 

 are active, the oxidation of this carbonate would complete a series 

 of reactions capable of forming the manganese deposits with which 

 we are dealing. It is very probable that these muds contained con- 

 siderable quantities of decomposing organic matter and were evolv- 



