282 J. C. BEAXXER OriLIXES OF THE GEOLOGY OF BRAZIL 



ful. and tlie Cretaceous probably does not reach that river on the west. 

 I have purposely omitted Katzer's distribution of eruptive rocks in the 

 State of Para. Data for such a map are not available in any part of 

 Brazil. Katzer's geologic map of Para should only be used in connection 

 with the text which it accompanies.'* The best original papers on the 

 geology of Para are those of Derby, Hartt. Smith, and Katzer. The 

 fossils are described by Clarke. Derby, and Eathbun. The geology along 

 the Oyapok and on the boundary with Trench Guiana is outlined in 

 Yelain's description of the rocks collected there by Crevaux. The out- 

 lines of the floodplain of the Amazon between 5i degrees and 56 degrees 

 are taken from Herbert H. Smith's map in his "'Brazil, the Amazon and 

 the Coast.*^ 



General geology. — The Amazon Eiver follows a synclinal trough across 

 the State of Para. The northern and southern parts of the State are 

 Archean, against which are deposited Silurian rocks on the north and 

 Devonian and Carboniferous on both the north and south sides. From 

 western Para the Paleozoic sedimentary beds extend into the State of 

 Amazonas, but they are not certainly known east of the Tapajos, on the 

 south side of the Amazon, or east of Eio Maecuru, on the north side, 

 though it seems reasonable to suppose that they do extend farther east on 

 both sides. Eocks of later, but of uncertaui, age are found at many 

 places through the middle of the valley. Following the coast north and 

 south of the mouth of the Amazon are horizontal sedimentary beds prob- 

 ably of Tertiary age. Fossils found at Pirabas and at other points on the 

 coast east of Salinas show that some of these beds are certainly Eocene, 

 as ^liss Matiry has pointed out. (See bibliography.) 



Economic geology. — Gold is found in the Archean area along the 

 streams that flow directly into the ocean from the Guiana highlands. 

 Limestones occur in the Carboniferous beds at Itaituba, and are reported 

 in the mountains of the southeastern part of the state. Very little is 

 known a? vet. however, of the geology of the southern part of th? State 

 of Para, and the economic geology is therefore necessarily unknown and 

 undeveloped. 



Geologic Maps of Para 



Ch. Yelain, 1885. — In 1SS5 '^L. Ch. Velain published in the Bulletin 

 de la Societe Geographique de France a paper on the geology of French 

 Guiana. •■'Esquisse geologique de la Guyane francaise.''" using the data 

 collected by Dr. J. Crevaux in his explorations. The article is accompa- 



■- F. Katzer : Grundzuge der Geologie des unteren Amazonas-gebietes. Leipzig, 1903. 



