BASEMAN, GEOGRAPHICAL D I ST RIB UTION IN SO UTH AMERICA 23 



chains in east central Brazil. I also believe that the above sierras origi- 

 nally formed part of the southern and western boundary of the great 

 Permian Inland Basin which will be considered in the following pages. 



I have relegated both the Sierras de Tandil and de la Ventana (as 

 Hauthal did several years ago) to the Brazilian system for the following 

 reasons : 



1. The Sierras de Tandil, de la Vantana, de San Luis and de Cordova, 

 like the Serra do Mar of Brazil, are characterized by an almost entire 

 absence of marine fossils and have no marine Tertiary and Mesozoic, 

 which is characteristic of the Andean complex. 



2. In general succession^ the Archean rocks of these sierras resemble 

 the Serra do Mar rather than the Andean system. 



3. These sierras are well separated from the Andean complex by 

 many elevations and depressions, some of which afford evidence of Meso- 

 zoic and Tertiary invasions of the sea. 



4. From the absence of fossils, it may be judged that these sierras 

 have remained almost stationary; and as a result, there is a striking 

 correspondence between their altitudes and these of Brazil and Guiana. 



It is possible from similar reasons that at least part of the Cordilleras 

 Oriental of the northern Andes will be shown to belong to the old Bra- 

 zilian system, but entirely too little is known about this region to war- 

 rant a consideration at this time. 



The trend lines of the Pacific side are also parallel to the coast. In 

 the region of La Paz, Bolivia, there is an indentation of the coast back 

 of which the chains of mountains are bent out of line and piled up to 

 several thousand feet of altitude. This region is, in a way, the counter- 

 part of the fan-shaped region of Pernambuco along the Atlantic Coast. 

 In other words, the trend lines of the two coasts exhibit a. remarkable 

 similarity, as is indicated in a general way on Plate XL The only strik- 

 ing difference is than in the region of La Paz, Bolivia, the coast is bent 

 in, while it is bulged out in the region of Pernambuco. Taylor . has 

 attempted to explain part of this by a sliding of the Brazilian mass 

 against the Andes. This sliding was assumed to be due to some force 

 applied parallel to the Brazilian coast but having a greater intensity in 

 the regions of the mouths of the Amazon and la Plata. 



The lines of weakness and strength in a general way extend north and 

 south (as Schuchert has shown for North America). This is shown by 

 the maps of the marine deposits. The invasions of the sea as a rule 

 appear to have been from the south toward the north. The Permian of 

 southern Brazil or the Devonian extending from the Amazon Valley 

 past Cuyaba into Parana, and perhaps as far south as Sierra de Tandil, 



