236 



C. E. LONG WELL — KOBER's THEORY OF OROGENY 



plates of the crust. The northern foreland is Eurasia, the southern a 

 combination of Africa, Arabia, India, and Australia. Intensity of over- 

 turning varies from place to place, as do the width of the orogen as a 

 whole and the distance between border ranges. The greatest of the inter- 

 montane masses forms the high plateau of Tibet. 



Comparison of the Mediterranean Orogen with other Mountain 



Systems 



^Ye may say, then, that the Mediterranean orogen exhibits bilateral 

 symmetry in section, and its ranges are grouped systematically in ground 

 plan. It will be well to examine other mountain systems for evidence 

 of similar relationships. Paleozoic mountains have been eroded, frag- 

 mented, buried. under later sediments, and therefore in many cases the 

 complete plan of their architecture is not evident. Thus in the Altai 



Figure 4. — Bloc'k diagrams eines mit einem Vorlande einseitig versenkten Orogen 



Kober's figure 33, page 167. 



Mountains we see overturning to the north, over the old Siberian table, 

 but farther to the south the structures are obscured, due to later 

 deformation. In the Urals a partly resurrected Paleozoic system, folds^ 

 and "decken'^ reaching both east and west are exposed, conforming to 

 Kober's theory. A still better illustration is found in the post- Silurian 

 Caledonian Mountains, represented on one side by the great Scandinavian 

 overthrust to the east and on the other by the Scottish overthrusts to 

 the west. The middle portion of the orogen has sunk beneath the sea. 

 We turn now to the Western Hemisphere. Kober has read of struc- 

 tures overturned westward along the Pacific coast of North America, 

 and of the Eocky Mountain overthrusts to the east. He seeks to join 

 these widely separated features to form a single orogenetic zone. Those 

 who are familiar with the mountains of western North America will not 

 consider this interpretation seriously. It appears, however, that a sug- 

 o-estion of Kober's plan exists on a more limited scale in the Jurasside 

 structures of California and Nevada, which exhibit overturning to the 



