The Serra Do Espinhaço, Brazil

Abstract

The name Serra do Espinhago ("Backbone Range") was introduced into geographical literature in 1822 (i) by the founder of Brazilian geology, Wilhelm von Eschwege, as a comprehensive term for the various orographic units that form a great watershed between the rivers flowing directly to the Atlantic and those that discharge first into the Uruguay, Parand, and S-o Francisco. By modern usage, and in fact by the subsequent usage of Eschwege himself, the name has, however, been practically limited to the section of this watershed corresponding to the Sao Francisco basin, the greater part of that corresponding to the Parana basin being known as the Serra da Mantiqueira, while the remainder of this section and the one corresponding to the Uruguay basin are considered as forming parts of the Serra do Mar range. As thus limited, the name, though robbed of much of its pristine importance and appropriateness, is applied to a well-marked orographic feature distinguished by special topographic, geologic, and tectonic characteristics. Some of the most distinctive topographic and geologic features of the range are well set forth by Eschwege in his detailed descriptions of his various journeys in the gold and diamond districts (2) comprised in the section extending from Ouro Preto to Diamantina, the occurrence of these minerals being of itself one of the leading characteristics of the range. Thus he contrasts the greater mean elevation (1,000000 with peaks rising to I,500-I,8OOm), the general plateau character with abrupt margins, the bald and rugged aspect of the peaks and minor ridges, and their general north-south trend, and the predominance of schistose rocks (especially quartz and ferruginous schists), with the lower altitude, gentler and apparently systemless topography ("like a storm-tossed forest sea") and predominance of crystalline rocks (principally gneiss and granite)' that characterize 1 Eschwege had a special crystalline-chemical hypothesis of his own (set forth in detail on pp. i ff. of his Gebirgskunde) regarding the mode of formation of what