68 CHARLES LAURENCE BAKER 



northern Santa Catharina/ Alluvial sandstones and shales, coal 

 beds and palustrine carbonaceous and bituminous shales, laid 

 down on low flattish surfaces, perhaps slowly sinking, followed. 

 These are the Rio Bonito beds of Uruguay,^ Rio Grande do Sul, 

 Santa Catharina, Parana, and southern Sao Paulo. The Rio 

 Bonito in Rio Grande do Sul, Uruguay, and southern Santa 

 Catharina rests, so far as known, directly on the basement complex, 

 often with relatively little basal conglomerate. Following the Rio 

 Bonito is the Palermo, a relatively thin formation of shales. Next 

 is the Iraty, also relatively thin, dark bituminous (sapropeHtic) 

 shales with some interbedded limestones and cherts, carrying the 

 fresh-water reptiles, Stereosternum and Mesosaurus (also found in 

 Cape Colony) and numerous ostracods. The Iraty appears to have 

 been a fresh-water lake deposit. It outcrops in a northeast- 

 southwest direction for about 800 miles, extending from northern 

 Sao Paulo to central Uruguay. The cycle was ended by the 

 deposition of clays with a few thin concretionary limestones, some 

 of which have fish and moUuskan fossils — the Estrada Nova beds. 

 All the deposits of this first depositional cycle have been referred 

 to the early Permian or "Permo- Carboniferous," but at least the 

 glacial and coal formations may prove to be late Pennsylvanian. 

 The total thickness averages about 1,650 feet (500 meters). 



An erosional unconformity intervenes between the sequence just 

 described and the overlying red beds. This unconformity, first 

 noted by I. C. White, was found by the writer in Sao Paulo, Parana, 

 and northern Santa Catharina; hence it probably denotes a time 

 break of considerable importance. The lower of the two red bed 

 formations, the Rio de Rastro — only 300 feet thick at the north 

 but apparently thicker in Rio Grande do Sul — has yielded in Rio 

 Grande do Sul a few reptihan remains^ which appear to indicate its 

 approximate contemporaneity with the whole of the Triassic part of 



^ Glacial beds may some time be foimd in Rio Grande do Sul. A likely area is 

 in the coimtry between Suspiro and Bage, particularly n«ar Ibare in the southern part 

 of that state. The best section of glacial beds now known in Brazil is along the Sao 

 Francisco Railway on the northern Santa Catharina border. 



^ The writer is indebted to Karl Walther's publications for numerous data on the 

 geology of Uruguay. 



5 The best-known collecting grounds are just south of Santa Maria and on the 

 Rio Grande-Santa Catharina border northeast of the seaport of Torres. 



