392 ORVILLE A. DERBY 



beds with the Tertiary series of the coast, and cited them as evidence 

 of a general uphft to the amount of about 1,000"^. There is, how- 

 ever, no evidence that they are of marine origin, and it seems much 

 more probable that they were deposited in a closed inland basin, 

 which extends for a long distance down the Jequetinhonha valley, 

 but is probably cut off from the lower-lying coast Tertiary series by 

 a high zone of older rocks. In this case the evidence of uplift is 

 given by the depth to which the valleys have been excavated below 

 the surface of these beds, rather than by their elevation above the 

 level of the sea, and its amount (2 5o±"') accords fairly well with 

 that indicated by the coast Tertiary beds themselves.^ The sandstone 

 beds are often quite thin, and probably nowhere more than 100™ 

 thick. 



The plateau to the west of the Serra do Espinhafo, with a general 

 elevation of 800 to 900™, also shows truncated folds, but the strata 

 here consist of shales, sandstone, and limestone thickly threaded 

 with quartz veins. Farther west, and near the Sao Francisco, appear 

 table-lands of horizontal sandstones and shales of about 800"" eleva- 

 tion. Silicified dicotyledinous wood occurs in some of these beds, 

 which are presumed to be of Cretaceous age. 



The central plateau, or Serra do Espinhafo proper, shows along 

 both flanks of the Diamantina section heavy beds of quartzitic sand- 

 stone, which dip sharply to the east on the eastern flank and to the 

 west on the western (11, 12). Over the central part the dips are 

 gentler and more variable, the beds in places being nearly horizontal. 

 Over large areas the sandstone has been completely denuded away, 

 revealing an underlying series of quartzites and argillaceous schists, 

 with in one place a considerable patch of granite. As in the Para- 

 guassu and Grao Mogol sections, there is here abundant evidence 



I See Branner (i8), who traced the coast Tertiary beds to the summit level of 

 the Bahia and Minas Railroad in the Serra dos Aymores. The altitude is not given, 

 as the railroad levelings were not obtainable, but by my aneroid readings it cannot 

 be much over 200™. x^long the Bahia and Sao Francisco Railroad, as noted above, 

 the Tertiary beds rise to 400™, or a little more; but here the upper portion is of fresh- 

 water origin, and perhaps much later than the lower beds, which correspond better 

 in character with those along the Bahia and Minas line. In the basins of the upper 

 Rio Doce in Minas Geraes, Tiete and Parahyba in Sao Paulo there are high-lying 

 fresh-water Tertiary basins, with fossils, that seem to correspond with the one 

 above considered. 



