344 E- C. HARDER AND R. T. CHAMBERLIN 



intrusives. These rocks form the basement complex of eastern 

 Brazil and are probably to be referred to the Archean. The 

 crystalline belt extends far into the interior, at first continuously, 

 but farther away from the coast, as patches and arms amid areas 

 of overlying post-Archean sedimentary formations. 



Eastern Brazil has been, throughout much of its geologic 

 history, a region more subject to denudation than to sedimentation. 

 In Minas Geraes the uncovered basement complex is now areally the 

 most extensive surface formation. The basal granite, gneiss, and 

 crystalline schist are nearly continuous throughout the eastern and 

 central portions of the state. Where the younger sedimentary 

 beds do occur, they persist in favored localities as local remnants 

 of former widespread formations. The post-Archean sedimentary 

 series is best represented within the limits of the Serra do Espin- 

 hago which owes its existence and present elevation to the superior 

 resistance of some of its quartzite beds. 



The area of post-Archean sedimentary rocks of central Minas 

 Geraes extends in a continuous belt of varying width from about 

 latitude 2o°4o' S., in south-central Minas Geraes, northwestward 

 across the state and into the state of Bahia. Southward from 

 latitude 20^40' S, isolated areas of sediments continue into southern 

 Minas. As a result of complex earth movements, the southern end 

 of the principal sedimentary belt is wide and irregular, occupying 

 nearly all of the area from a point about 15 kilometers southeast 

 of Ouro Preto, northwestward to Bello Horizonte, a width of about 

 80 kilometers. Followed northeastward the belt narrows but con- 

 tinues as a strip from 5 to 20 kilometers in width almost to Diaman- 

 tina, where it branches, one limb running northeastward into 

 northeastern Minas Geraes and the other continuing northward 

 into Bahia. Both on the east and west, this strip of sediments is 

 bounded by extensive areas of older rocks, probably Archean, con- 

 sisting of gneiss, granite, and crystalline schists. Areas of sedi- 

 ments, of unknown age, however, occur at various places west of 

 the sedimentary belt, becoming more extensive toward the north. 



The metamorphosed sediments, which Derby has called the 

 Minas series,^ are probably 01 Algonkian age, judging from their 



' O. A. D.erby, "The Serra do Espinhago, Brazil," Jour Geol., XIV (1906), 396. 



