392 E. C. ANDREWS THE HYPOTHESIS OF MOUNTAIN FORMATION 



These features are illustrated well in Australia, as elsewhere. ^^ 

 Excellent examples of the relatively narrow strips of folded sediments 

 of the Cenozoic occur within regions embracing the Alps, the Himalaya, 

 Xorth America, and elsewhere. 



For the Alps the close folding of the Molasse and the Flysch^"^ pass 

 within short distances into the horizontal beds of "the same age lying to 

 the north in Germany and France. This feature is well illustrated also 

 in the Himalayan region, both to the north and the south, the zone of 

 close folding being narrow. In America, from the works of Lawson, 

 Ransome, Tangier Smith, Le Conte, Diller, Lindgren, and others, it 

 would appear that the very narrow zones of the folded Cenozoic along the 

 Pacific margin pass inland into plateau and interplateau troughs, the 

 margins being warped and faulted, while in the great plains of the center 

 the Cenozoic lies horizontally. In Australia the edges of the coastal 

 plateaus are warped and faulted. Low pressure ridges lie in front of 

 these coastal and inland plateaus, but are of negligible width. 



Relation of Areas of Sedimentation to Mountain Ranges 



An examination of the great folded areas of the world indicates the 

 close relationship which has existed always between areas of great sedi- 

 mentation and of later mountain formation. In illustration of this point 

 it is only necessary to mention the mountains of the Archeozoic and the 

 early Proterozoic periods, as those also of the Appalachian, Himalayan, 

 and Alpine regions. In some, as in the area of the Grand Canyon, the 

 Archeozoic sediments were folded closely and subsequently denuded to 

 the very core of the great mountain systems. The immense thickness of 

 the sediments of the Algonkian which were deposited upon the planed 

 surface within the Archeozoic was raised later into lofty ranges of the 

 fold type. These in turn were removed by denudation in great measure, 

 and through the succeeding ages received the slow and steady sedimenta- 

 tion of the Cambrian, Ordovician, later Paleozoic, Mesozoic, and Ceno- 

 zoic periods, producing a total of many thousands of feet of sediment. 

 During the Cenozoic this mass was lifted gently to form plateaus, the 

 movement being revived several times without folding, as the term is 

 generally understood. 



Other regions, as the Himalayan,^^ after a long period of Mesozoic 

 sedimentation, experienced a powerful folding during the late Cretaceous, 



" E. C. Andrews : Journal of Geology, lOlG. 

 "P. Lake: The Al'js. Encyc. Brit., Ed. 11, vol. 1. 

 ''^ P. Lake: Encyc. Brit., Ed. 11. vol. 13. Himalaya. 

 Also, Wadia : Geology of India. 



