BRANNER: THE STONE REEFS OF BRAZIL. 27 



that they are newer than the Cretaceous and probably of Tertiary must 

 be taken for what it is worth, until the question is settled by palaeon- 

 tological evidence," ^ and that is about all one can make of the matter. 

 If we grant that the upper Amazon region from Iquitos to Tabatinga is 

 Tertiary, there is no evidence that the mottled sediments of the lower 

 Amazon are of the same age, to say nothing of correlating them with 

 similar-looking beds on the coast of Rio Grande do Norte, Parahyba, 

 Pernambuco, and Alagoas — 2500 miles away. This seems also to ex- 

 press Professor Derby's view of the subject.^ They are too far from the 

 region discussed in this paper, and too little is known of the interven- 

 ing country, for us to be able to connect the two. 



The later Tertiary deposits. — It seems proper to accept the general 

 trend of the evidence that some of the Brazilian coastal sediments are of 

 Eocene Tertiary age. At about a dozen known localities between A^ic- 

 toria and Natal these Eocene or some of the older rocks have resting 

 upon or against them a series of soft and generally dark-colored sedi- 

 ments that are probably of Pliocene age. These later sediments, whether 



•■•/I'i^^gaai^liajVsJ^fefe.S-^a^, ^';^d 



Fig. 5. Geologic section on the beacli of the Cunhahii Valie\-. 



Pliocene or not, throw important light upon the geographical and geo- 

 logic history of the coast, and for that reason the notes made upon the 

 exposures are here given. That more facts are not at liand is due to a 

 great extent to the uncultivated and jungle-covered condition of the 

 country. The forests are thick and practically impenetrable the year 

 round. The few known exposures, it will be observed, are all on the sea- 

 shore. It is reasonable to suppose that these same rocks occur pretty 

 much all along the coast, but they are difficult to find even when one can 

 get into the vicinity of them. 



Between Kio Cunhahii, S. lat. 6° 20', and the bluflfs at Bahia Formosa 

 is exposed along the beach a dark brown or snuff-colored soft false- 

 bedded sandstone. Tlie lower part of these beds is waslied by the tides, 



1 Bulletin Buffalo Soc. Nat. Hist, Jan. 1874, I., p. 235. 



- 0. A. Derby. A contribution to tlie geology of the Lower Amazonas. Proc. 

 Anier. Phil. Soc, 1879, XVIII., p. 176-177. 



