22 ANNALS NEW YORE ACADEMY OF SCIENCES 



granites are in the larger part of an age younger than the Ceara series and 

 somewhere along in the Devonian is entirely probable. You see between the- 

 Cambrian and the Cretaceous in the northern region we have no record. 



"It is entirely possible that the northern fan is due to local folding, but it is- 

 pretty large for that, that is to say, spread over a very large area." 



I believe that these facts indicate that no Paleozoic wedge or land- 

 bridge could have existed between this portion of Brazil and Africa,, 

 because the trend lines fade away toward tho sea, and there is no evi- 

 dence of the continuance of the lines across the Atlantic into Africa. 

 The folds are crushed and irregular and do not end abruptly along the 

 coast. Besides, if the wedge had existed, this type of fanlike folding 

 would, I believe, have been almost if not quite impossible. This fan- 

 like structure may possibly have been produced by some unknown force- 

 pushing from the interior of the earth at an angle to the vertical and. 

 more or less parallel to the coast, but more strongly in the region of the 

 mouths of Bio Amazonas and Bio de la Plata, if the Brazilian coast was- 

 not connected with Africa. This would have pushed the southern and. 

 northern ends of South America to the west and have made the "Per- 

 nambucan fan" on the east and a somewhat similar structure in the region 

 of Lake Titicaca east of the Bay of Arica. 



In southern Brazil and more especially in all of the Piano Alto, ero- 

 sion and extensive continental deposits have so disfigured the unexplored, 

 forested surfaces that little is known concerning the trend lines, but 

 superficially this region looks like an abruptly chopped-off coast. This 

 abruptness, I believe, is due to erosion of late and post-Paleozoic land 

 deposits and not to post-Paleozoic faulting. The northwest strike from 

 Cuyaba past the Madeira Falls, noted by Evans may be due to ancient 

 erosion, but I hardly think so, because the Piano Alto dips toward the- 

 southwest. The old drainage was into the East Andean Sea and hence 

 the rivers at that time cut the Piano Alto in a western-southwestern 

 direction. When the Amazon became reversed, Bio Madeira cut these- 

 old planes of erosion almost at right angles, producing thereby a very 

 complicated topography. 



By means of the trend of the Sierras de Tandil and de la Ventana, we 

 can separate both of them from the Andean complex, in spite of the fact 

 that Suess and Stelzner have been inclined to consider the Sierra de la. 

 Ventana as belonging to the Andean system. 



In fact, the writer considers that the Sierras de la Ventana and Tandil. 

 with all of their side chains are the southern extension of the Cordova. 

 Mountains by the way of Sierra de San Luis, where there is a break in 

 the system, just as the Serra do Mar of Brazil breaks up into several 



