woodworth: geological expedition to brazil and chile. 49 



border of the Triassic formation thus constituted is deeply notched by 

 the greater rivers, such as the Iguassu. The escarpments lying like 

 great loops on the eastern limits of the formation between these river 

 valleys receive various names such as the Serra Geral, the Serra da 

 Esperanfa, etc. Siemiradzki in a section reproduced b}' Suess gives 

 a somewhat different interpretation to the trap mass of the Serra da 

 Esperan9a, but the section of the same field credited to Derby is in 

 harmony with the structure here described as is also the section 

 traversed by the waiter between Rio Negro and Lages in Santa 

 Catharina. Further consideration of the Triassic rocks and their 

 bearing on the climatic conditions succeeding the Permian glacial 

 epoch are reserved for a following chapter. 



The Tertiary Deposits. — Whether or no the Cretaceous deposits 

 covering the border of the continent south of the Amazon have 

 representatives now in some of the sands and clays of the coastal 

 border south of Rio de Janeiro, there are rather recondite reasons for 

 believing that such deposits may once have flanked the coastal slope 

 of the Serra do Mar province; if so they were not long after their 

 deposition worn away. On the upland or planalto, to use the Brazilian 

 name of the plateau region, no known deposits occur between the 

 Trias and certain sediments in Sao Paulo which from their fossil 

 fishes are shown to be of fresh-water origin and Tertiary in age. These 

 deposits are most extensively developed in the valley of the Parahyba 

 between the Serra da Mantiqueira and the Serra do Mar and in a 

 smaller tract underlying the city of Sao Paulo. In these cases, the 

 beds occupy not well understood depressions in the Pre-Devonian 

 terrane. In what follows on the topography of the plateau, the 

 occurrence of these non-marine deposits will be advanced as evidence 

 of a change of attitude of the region in late Tertiary times. 



General Structure of the South Brazilian Permian Area. It remains to 

 describe the general structure of the region embracing the states from 

 Sao Paulo southward to Rio Grande do Sul. A glance at the geologi- 

 cal sketch map, Plate 15, shows that this region has been warped 

 in Post-Triassic times. A broad synclinal structure w^ith its axis in an 

 east and west direction occupies southern Santa Catharina and 

 northern Rio Grande do Sul, causing the Permian and Triassic in turn 

 to approach the Atlantic coast; and, because of the depression of the 

 beds towards the synclinal axis, they attain sea-level and in the 

 case of the Permian descend below that level. On the north of this 

 structure a complementary anticlinal axis is less well defined in central 

 eastern Parana. Its position is marked out by the arcuate trend of 



