72 CHARLES LAURENCE BAKER 



The minimum thickness of the basalt flows, not including what 

 has been removed at the top by erosion, is more than 2,000 feet 

 (White) in the Serra Geral between Lages and the Tuberao Basin 

 in Santa Catharina, 1,550 feet in northeastern Santa Catharina 

 (according to Woodworth),^ i ,300 feet at Porto Uniao on the Parana- 

 Santa Catharina border, 800 feet in the Serra do Esperanga between 

 Imbituva and Guarapuava in south-central Parana, at least 1,150 

 feet not including the basal portion at Porto Santa Helena on the 

 Rio Parana on the west boundary of the state of Parana, 1,150 feet 

 without the basal portion at MarcelHno Ramos on the Rio Uruguay 

 on the Santa Catharina-Rio Grande do Sul border, probably 1,000 

 feet or more north of Santa Maria, Rio Grande do Sul, at least 

 750 feet without the basal portion at Santa Rita on the Paranahyba 

 River on the Goyaz-Minas Geraes border, at least 600 feet without 

 the basal portion at Jatahy, southern Goyaz, and 400 feet in the 

 Serra do Itaquery in central Sao Paulo. These figures may indicate 

 that the thickest flows are in Santa Catharina, Parana, and Rio 

 Grande do Sul, but such a generalization is untrustworthy because 

 of the erosion varying in amount from place to place. 



Lithology. — The lower sheets intercalated with relatively thick 

 beds of Sao Bento sandstone are for the most part not included in the 

 thickness given above. These are either flows interbedded with the 

 sandstones, or are intruded as sills. It is often difficult or impos- 

 sible to choose between these two alternatives since some of the rocks 

 known to be flows have as dense a texture as those known to be 

 intrusives, and the silicified sandstones of the Sao Bento, inter- 

 calated between these lower sheets, may have been hardened by 

 flows or cemented and partially "metamorphosed" after the 

 volcanism, for instance by the mingling of underground waters. 

 There is usually some intercalated sandstone, in relatively minor 

 proportions, in the upper main mass of the lava, but in Santa 

 Catharina and western Parana no intercalated sandstone was 

 detected in more than 600 miles of traverse. There is accordingly 

 some likeUhood that these upper sandstones are more abundant 

 near the periphery of the original lava field. 



' Geologic Exploration in Brazil and Chile, Bull. Comp. Zool., Harvard CoUege. 



