HAS EM AN, GEOGRAPHICAL DISTRIB UTION IN SO CTH AMERICA 33 



coast) and that (?) Archean rocks underlie the alluvial deposits of the 

 Amazon and are continuous with the basal rocks of the highlands on 

 both sides of the Amazon. 



The writer has independently, and from a slightly different stand- 

 point, arrived at the same general conclusion, namely, that the Amazon 

 is a reversed river, but he differs with Katzer in regard to the following 

 details : 



1. The writer does not believe that there is any geological evidence 

 which even vaguely suggests either the existence or the submergence of 

 the hypothetical land-mass to the east and north of the present mouth of 

 the Amazon Eiver. In fact, just south of the mouth of the Amazon 

 are marine Cretaceous fossils which indicate a slight elevation of the 

 present mouth of the Amazon from the sea and not a continuation to 

 the east with a hypothetical land-mass. 



In this connection, no support for the hypothetical old land-mass can 

 be derived from the Barbados Islands, because they are entirely too far 

 to the north and belong to the Antillean complex. Both the absence of 

 islands and the deep-sea soundings are strong evidence that, previous to 

 the Miocene, no land existed east and northeast of the present mouth of 

 the Amazon across the Atlantic Ocean. 



In fact, there is no necessity for the assumption of the submergence 

 of any great mass of land to the east of the present mouth of the 

 Amazon, not even to form a watershed, because many rivers, like Eio 

 Parahyba, Eio Tiete, Eio Iguassu, etc., of southeastern Brazil, rise within 

 a few miles of the Atlantic Ocean and then flow several hundred miles 

 before entering it. 



2. The reversal of Eio Amazonas from the region of Eio Pani is 

 roughly comparable to the supposed reversal of the Mississippi from the 

 region of New Orleans instead of nearer its headwaters. That is to say, 

 the comparatively recent reversal of the Amazon will have to be. I think, 

 in th<3 region where the most of its large affluents enter it, namely, some- 

 where between Manaos and Santerem; because Eios Madeira, Solomoes 

 and Negro, which make the main stem of the Amazon, come together 

 just below Manaos. There is topographical evidence which shows that 

 the Eio Negro formerly entered the Eio Solomoes above its present 

 mouth, and hence the eastward extension of its mouth indicates that its 

 present mouth is near the region where the Amazon began to cut through 

 the old watershed, i. e., near the dissected western base of the original 

 Piano Alto which has been washed away by the Amazon. 



The arrangements of the low secondary sierras in the region of the 

 lower Eio Tapajos on the south side and near Obidos on the north side 



