208 J. C. BRANNER OUTLINES OF THE GEOLOGY OF BRAZIL 



vonian, see the titles under those States by Clarke, Katzer, Kayser, Oli- 

 veira (Euzebio de Paulo), Eathbun, Schuchert, Smith, Vogel, and Von 

 Ammon. 



In the Amazon region the Devonian rocks are white and yellowish 

 sandstones and black and reddish shales. Along the north side of the 

 Amazon they are exposed from just north of Almeirim westward to Eio 

 Uatuma, a stream between the Trombetas and the Negro. They dip 

 toward the Amazon at a low angle — about five degrees. At Erere and 

 elsewhere they are cut by dikes of diabase. South of the Amazon the 

 Devonian rocks are believed to be exposed on Eio Maueassu south of 

 Laranjal, and on the Tapajos south of Itaituba ; but no fossils have yet 

 been found in these particular areas, and there is, therefore, doubt about 

 their precise age.^ 



In Parana and southern Sao Paulo the Devonian rocks seem to rest 

 directly on the Brazilian complex and dip gently westward beneath the 

 Permian. The rocks are conglomerates, sandstones, and shales. The 

 diamonds found in Parana are supposed to come from the basal conglom- 

 erate. In Matto Grosso the Devonian rocks are sandstones and shales 

 resting unconformably on rocks of the Brazilian complex and dipping 

 gently eastward. In Bahia the Caboclo shales of Branner are supposed 

 to be Devonian, but thus far they have yielded no fossils.^° 



Economic geology of the Devonian. — The Devonian rocks contain the 

 conglomerates of Parana from which the diamonds of that state are sup- 

 posed to be derived. 



The Caboclo shales of the interior of Bahia are available for the manu- 

 facture of Portland cement. 



Elsewhere the Devonian beds are not known to contain anything of 

 special economic importance. 



CAnBOXIFEROrS 



General observations. — Fossiliferous Upper Carboniferous beds are ex- 

 posed on the lower Tapajos in the State of Para, and on some of the 

 smaller streams to the west of Tapajos, notably at Pedra do Barco and at 

 Frechal, and also on the northern side of the Amazon on the rios Uatuma, 

 Jamunda, and Trombetas. The geology and fossils are described by 

 Chandless, Derby, Katzer, Ossat, and Tschennede. 



All of the Brazilian rocks certainly knowai to be of Carboniferous age 

 belong to the Upper Carboniferous and are confined to the areas men- 

 tioned. Other areas shown as Carboniferous on Katzer's map of Para 



» F. Katzer: Geologic des T'ntereii Amazonas Gebietes. p. 215. 



^° Geographical Journal, August, 1911, pp. 151, 258 ; Amer. Jour. Sci., vol. xxxi. June, 

 1911. p. 481. 



