74 CHARLES LAURENCE BAKER 



Parana Basin, but the slope may be entirely or in large part deposi- 

 tional. The supra-basalt formation much resembles in character 

 and mode of origin the later Cenozoic deposits of the Llano Estacado 

 of Texas and New Mexico, and like the latter may be of widely 

 different ages at different localities. The only other supra-basalt 

 deposits, besides stream alluvium, yet known, are sediments, prob- 

 ably eolian, of the Pampean loess in northeastern Argentina, western 

 Uruguay, and southwestern Rio Grande do Sul. 



Age of the basalt flows. — ^Assuming that the age of the upper 

 part of the Rio do Rastro red beds is that of the Beaufort beds of 

 the upper Karroo of South Africa, with which they are correlated 

 by Smith- Woodward, and that the Bauru dinosaurs belong to the 

 Wealden, we have an interval between some stage of the Triassic — 

 presumably later Trias — ^and the beginning of the Cretaceous, 

 during which there were (i) deposition of the Sao Bento sandstone, 

 (2) the outflow of the basalt, (3) the deformation of the lavas, and 

 (4) a subsequent period of erosion. This would indicate most 

 probably that the basalt eruptions fell within the Jurassic, possibly 

 in the upper Triassic. There is, perhaps, some reason for uncertainty 

 concerning the exact stage of the Trias occupied by the upper Karroo 

 of South Africa and the upper Rio do Rastro of the Parana Basin. 

 At a time more or less the same as the deformation of the lavas 

 and formation of the Parana geosyncKne, there were formed basins 

 in the crystalhne area of easternmost Brazil which became sites of 

 deposition of Cretaceous and early Tertiary marine sediments. 



Perhaps contemporaneous was the formation of the long trough 

 within the basement complex which parallels the Atlantic coast 

 line from Campos in easternmost Rio de Janeiro state, to Curityba 

 in Parana, followed by the valleys of the Parahyba, the upper 

 Tiete, the Iguape, and Ribeira and covered by Tertiary lake 

 deposits along the upper courses of the Tiete and Parahyba. 



Near the time or contemporaneous with the basalt eruptions 

 there was formed the eastern pre-Andine and eastern Andine 

 depositional basin, in which marine sedunents were deposited 

 throughout the Jura and part of the early Cretaceous, and conti- 

 nental sediments during the later Cretaceous and Cenozoic. The 

 epoch of outflow of basalt occurred at or near the time of breaking-up 



