THE SERRA DO ESPINHA^O, BRAZIL 



ORVILLE A. DERBY 

 Sao Paulo, Brazil 



The name Serra do Espinhajo ("Backbone Range") was intro- 

 duced into geographical hterature in 1822 (i) by the founder of 

 Brazihan 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, Parana, and Sao 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 hmited, 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) com- 

 prised in the section extending from Ouro Preto to Diamantina, the 

 occurrence of these minerals being of itself one of the leading char- 

 acteristics of the range. Thus he contrasts the greater mean eleva- 

 tion (i,ooo"^± with peaks rising to 1,500-1,800"^), 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 ("hke 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. ii ff. of his Gebirgskunde) regarding the mode of formation of what 



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