196 J. C. BR-VXXER OUTLIXES OF THE GEOLOGY OF BRAZIL 



This Statement is necessary because the map may otherwise seem to be 

 more detailed than the published data seem to warrant. 



Xext after my personal observations and those of my assistants I have 

 sought the original sources of all trustworthy information about the 

 geology of Brazil — iiiformation scattered through books of travel and 

 even through the daily newspapers of that country, as well as through the 

 scientific publications of all parts of the world. 



The observations of some of the early geologists have been made diffi- 

 cult by their use of certain terms. The word '^itacolumite.^* for example, 

 has been especially confusing, while the words •'^uebergangschiefer,*' 

 traumatic shales, ^'formation phylladienne."' and such like expressions 

 keep one in constant doubt about the precise meaning of the authors 

 using them. 



The text accompanying the geologic map of Brazil is not intended to 

 explain or give details regarding the geolog}'. but simply to provide a 

 brief condensation of what is known and to enable those who use the map, 

 or who seek information about the geology of Brazil, to start with a fairly 

 clear idea of what is known, and to obtain at first hand all of the pub- 

 lished information that exists in regard to the geology of the country and 

 of each state. 



In view of the limitations of our knowledge, it is not possible to repre- 

 sent on the map more than thirteen subdivisions of the geologic column. 

 In some localities many more subdivisions are known and over a limited 

 area might have been shown, but there would be no particular object in 

 giving all of these subdivisions on a map of this scale. The minor details, 

 even where they are known, are necessarily omitted on account of the 

 smaU scale of the map. In regions of horizontal rocks where partings are 

 dendritic in form and outliers are abundant, these features can not con- 

 veniently be shown. The areas of old crystalline schists are almost every- 

 where traversed by dikes of eruptive rocks, but these dikes are usually 

 too small to be shown on a map of the scale of this one. The same thing 

 ]? true in the southern states, where numerous dikes cut all of the rocks 

 below the Cretaceous. 



Inasmuch as interest in the geology of Brazil is likely to be more or 

 less a special interest in some particular branch, it seems worth while to 

 refer to the available sources of information in regard to the different 

 branches of geology, such as economic geolog}\ paleontologv, petrography, 

 etcetera, and to other matter that geologists may need to know. 



Many of the books and papers cited are not only not on geologv. but 

 they contain very little geological information : but the strav notes of a 



