396 



E. C. HARDER AND R. T. CHAMBERLIN 



The iron formation has all the characteristics of a sedimentary 

 deposit, although, just as in the rest of the Minas series, fossils 

 have not been recognized in it. Portions are very massive and 

 exhibit little or no evidence of bedding, as is frequently seen in 

 massive quartzites, while other portions are thin-bedded or finely 

 laminated, as shales and fine-grained sandstones. In the thinner- 

 bedded portion the bedding or lamination planes are for the most 



Fig. i6. — The Fazenda de Alegria. The highest peaks behind are of Caraga 

 quartzite. The strong range of hills in- front are of iron formation. To the left of 

 the deep notch they are chiefly of itabirite; to the right of it dominantly of laminated 



part sharply defined. The stratification in places is rendered very 

 conspicuous for the reason that in the itabirite portions of the 

 formation the iron-oxide layers are so frequently separated by thin 

 partings of white quartz sand. These sandy partings, as planes of 

 weakness, control to a considerable extent the weathering and 

 fracturing of the beds. While the main bulk of the iron formation 

 consists of sandy iron-oxide-bearing beds, there frequently occur, 

 interbedded with these, shaly or schistose iron-oxide-bearing beds 



