26 ANNALS NEW YORK ACADEMY OF SCIENCES 



and west structural lines, the deep intervening sea, absence of islands, 

 relative evenness of great ocean depths, the absence of the deposits found 

 in deep seas on the continental shelves and the shape and abruptness of 

 the coast due to ages of erosion assisted by recent elevations, we conclude 

 that South America could hardly have been connected with the eastern 

 hemisphere. 12 



PLANO ALTO AND THE PERMIAN INLAND BASIN 



I have used the native term, Piano Alto, to include all of the sand- 

 capped tableland which extends south from the Guianas through Brazil 

 into Uruguay and west into Bolivia. The outlines of this region are 

 shown on Plate XII. All of these highlands appear to have been deposited 

 in a fresh-water inland basin during the Permian epoch. The remains 

 of Permian reptiles (Mesosaurus and Stereo sternum) , of the Gondwana 

 flora and other plants, of Scaphonyx, a Triassic reptile, of Schizodus, 

 Conocardium, Myalina and a few other marine iamellibranchs found in 

 the highland region indicate that the Piano Alto was deposited by wind 

 and rivers in a fresh-water inland basin of Permian age- The thin layer 

 of "intercalated marine limestone indicates only a brief Permian in- 

 vasion of the sea in the Piano Alto of southeastern Brazil. 



The Permian Inland Basin was almost surrounded by Archean moun- 

 tains : on the east by Serra do Mar and its northern spurs ; on the south 

 and west by the Cordova Mountains and their southern spurs; on the 

 north by Archean rocks of Guiana and Venezuela, and on the north- 

 west perhaps by the Cordillera Oriental. The characteristic sandstone 

 found in all of this region was in part deposited in shallow fresh water 

 and in part shuffled about by winds into this Permian basin. 



The basal Piano Alto formation or the floor of the Permian inland 

 basin is composed of granites, gneisses, crystalline schists and the like, 

 which are generally considered pre-Cambrian or Archean, because of 

 the absence of fossils. On various portions of this basal formation are 

 Paleozoic deposits which have already been mapped, but which will 

 without doubt be greatly extended as exploration proceeds. These maps 

 show that none of the Piano Alto included in Plate XII has been invaded 



12 The absence of marine Lower Carboniferous fossils from eastern Brazil is not, in my 

 opinion, nearly as strange as the apparently entire absence of post-Paleozoic marine de- 

 posits of southeastern Brazil, in view of the fact that west of Serro do Mar are found 

 marine deposits of Devonian and Permian age. The first great escarpments in British 

 Guiana, not far from the coast, are due to the erosion of the Piano Alto sandstone in the 

 regions of the Kaieteur Falls ; similar conditions exist right along the coast of south- 

 eastern Brazil. So it will take far better evidence than exists to prove that this coast 

 of Brazil is a post-Paleozoic faulted one and not a Paleozoic one which has remained 

 stable and has been changed by the erosion of later land sediments. 



