IIO NEW YORK STATE MUSEUM 



flexure of the chains performed by the southeast Asiatic fold system 

 between continental Asia and Australia. 



For the present, we therefore believe the evidence is not sufficient 

 to claim the Precambrian age of the east-west direction of the folds 

 of that system or for the assumption of the existence of a separate 

 Precambrian earth segment in the East Indian Archipelago. 1 



/ Precambrian Fold System of South America 



It has long been known that South America is built on essentially 

 similar lines in its present framework as North America. Suess 

 (v. 2, p. 139 of English trans.) has pointed out that not only the 

 Cordilleras of the west are the result of an identical movement 

 but he also states, following Derby, that the Predevonian mountain 

 chains of the east are built so that " the older rocks lie toward the 

 east, and the folding movement was directed toward the interior " 

 and that this important observation " assigns the Serra do Mar in 

 the continent of South America a position similar to that occupied 

 in North America by the Appalachians." 



Between these marginal fold systems we find again, as in North 

 America, a great Precambrian basement complex, " die alte brasilische 

 Masse " as Suess calls it, largely covered by younger formations, 

 but still exposed over immense areas. 



Branner (19 19, p. 203), in his comprehensive " Outlines of the 

 Geology of Brazil to Accompany the Geologic Map of Brazil " has 

 pointed out our present great lack of knowledge of this great basement 

 complex. He writes: " The rocks referred to the Archean in Brazil 

 are granites, gneisses, quartzites, marbles and crystalline schists. 

 Too little is known of these old rocks at present to warrant such 

 a separation of them as has been made of similar rocks in North 

 America; for that reason they are called the Brazilian complex. . . . 

 But little is known of the structure of the Brazilian complex. 

 Much information on the subject is scattered through the literature, 

 but widely separated areas can not be confidently tied together with 



1 J. Wanner (Die Geologie von Mittel-Celebes nach den neueren Forschungen 

 E. C. Abendanons und anderer. Geol. Rundschau, 10:45, I 9 I 9) nas meanwhile 

 claimed that Abendanon's inference of an east-west mountain system of Pre- 

 cambrian age is based on insufficient data, since most observations fail so far 

 to indicate a regularity or constancy in the strike of the Precambrian rocks. 

 The hypothesis of an east-west fold system is, according to Wanner, not supported 

 by the boundaries of the gneiss-granite and schists, which have northwest- 

 southeast directions and by the results of Abendanon's journey which show 

 that in the schists always younger zones appear from west to east, indicating 

 a general north-south trend of the folds. 



* It will be noted that if Wanner is right in his conclusions, particularly the 

 last mentioned, Aequinoctia clearly falls in with the general Precambrian fold 

 direction of Africa, India and West Australia and probably was a part of the 

 a ncestral Gondwana land, as we had believed before seeing Abendanon's paper. 



