412 THE CKETACEOUS AND TERTIARY GEOLOGY 



Part III. 



THE TERTIARY. 



The thorough understanding of the tertiaiy geology of Brazil, not to say of 

 South America, would, in my opinion, be of more interest and value to geology than 

 that of any other geologic horizon represented on that continent. A full discussion 

 of it cannot be undertaken here, is not intended, and indeed would be impossible with- 

 out a vast amount of field work. The formation is too widespread and the questitms ■ 

 presented by it too complicated to admit of discussion in this place, further than it 

 relates to the geology of the Sergipe-Alagoas basin and to the cretaceous formations 

 of the eastern coast. 



In Brazil this formation is represented by horizontal beds of sands and clays form- 

 ing a system of marine terraces from 100 to 250 feet thick, extending from some- 

 where between Eio de Janeiro and Bahia more or less continuously along the coast 

 to the north, being especially prominent fi'om about Maeeio nearly to Cape St. Roque. 

 In the Amazon valley they form the table-topped hills and are widespread from the 

 Rio Araguay westwai-d. The beds of the Amazon valley were thought by Agassiz 

 to have been deposited in an inland lake during the glacial epoch. Pissis says that 

 the marine tertiary beds of the coast are represented in the interior by beds of la- 

 custrine origin. The origin attributed to the tertiary by Prof. Agassiz need not be 

 discussed, as in all i^robability no one now admits its correctness, while a lack of 

 knowledge of the lacustrine deposits of the interior i-enders the discussion of the 

 theory of Pissis impossible. It must be admitted, however, that this theory of Pissis 

 is a very plausible one, and such observations as the writer has made upon the geol- 

 ogy of the interior of Brazil leads him to accept it as a favorite working hypothesis. 

 In none of the supposed tertiary beds of the interior, at least in the provinces of Rio 

 de Janeiro, Minas Geraes and Matto Grosso, has the writer found unquestionable 

 evidence of the tertiary age of such deposits.* 



Character of the Beds. — The general features of the Brazilian tertiarj' have been 

 several times described by such good observers as Agassiz and Ilartt. The uniformity 



* Since the above was written a letter, making inquiry concerning tlic tertiary, has been directed to Mr. James E. 

 Mills, of San Francisco, Cal., who has traveled in many parts of the interior of Brazil. In reply Mr. Mills says : 

 "I cannot give you any definite information from my notes about the tertiary deposits in Brazil, because in Rio Grande 

 do Sul, Minas Geraes, Rio de Janeiro, and other parts of the country where I had opportunities for observations and 

 study, there are no deposits which I know certainly to be of tertiary age." 



