U6 NEW YORK STATE MUSEUM 



by Paleozoic folding, which mainly occurred in the marginal regions 

 only, these Paleozoic folds on the whole correspond with or appear 

 to be controlled by the earlier Precambrian folds. 



It has been urged by the writer that these enormous areas of 

 uniform or continuous Precambrian fold directions represent Pre- 

 cambrian segments of continental size and the term arch-continents 

 has been proposed for these vast bodies in the preliminary paper 

 in the sense that they were ancestral to the later Paleozoic continents. 

 We shall now investigate the relations of these supposed Precambrian 

 continental masses to the recognized continents of Paleozoic time. 



Relations of Precambrian Continents to Paleozoic Continents 



Suess (Suess-Sollas, v. i, p. 600) has from his classical survey 

 of the present fold systems of the earth distinguished the following 

 units among the continents: 



" The first of these is I ndo- Africa, the greatest tableland of the 

 earth, limited on its northern border, from the point where the 

 Wady Draa discharges into the Atlantic ocean to the mouth of the 

 Brahmaputra, by the folds of Eurasia advancing to the south, but 

 elsewhere, as far as it is known to us, surrounded solely by faults 

 and divided in two by the Indian ocean. 



" The second unit is South America, a shield, as it were, girdled 

 on three sides by mountain ramparts ; broken off without perceptible 

 trend lines on the east and northeast, and with open virgation of 

 the branches of the mountains to the southeast between Cape Horn 

 and Cabo Corrientes. 



" The Cordillera of the Antilles shows a closer affinity to South 

 than to North America. 



" The third unit is North America; so far as folding is known in 

 this continent it appears to be everywhere directed to the west, 

 with a few exceptions caused perhaps by local overthrusting on to 

 the subsidence at the outer border of the Rocky mountains; this 

 westerly movement began in extremely ancient times, and manifests 

 itself from the Atlantic coast to the Pacific, from the Appalachians to 

 the Sierra Nevada and the coast chains. Toward the north, however, 

 a very extensive ' plate ' without folding appears, which stretches 

 nearly to the Arctic Archipelago. . . 



" Least obvious as an organic whole, notwithstanding the extra- 

 ordinary magnitude of the folded area on its southern border, is the 

 unit of Eurasia. Here we are in the presence of much greater com- 

 plexity and diversity; the description of its various parts is not 

 yet advanced far enough to enable us to bring it into comparison 

 with the other continents. For the same reason I must provisionally 

 pass over Australia 1 in silence." 



1 Australia is shown by Suess in the fourth volume to be a remnant block 

 surrounded by three arches of the Oceanides in the east. 



