368 



DYNAMICAL GEOLOGY. 



flexure, and the thinning, even to removal, of those of the flanks in close- 

 pressed overthrust flexures, are two important points well illustrated in 

 Figs. 118 and 119 on page 110, and in Fig. 120, representing the resulting 



341. 



Section of the Jura Mountaing, along a line extending northwestward frona Geneva through St. Claude 

 to Chaux du Dombiel. 1, Trias ; 2, Lower Jurassic ; 3, Upper Jurassic ; 4, Cretaceous ; 5, Tertiary. 

 Scale, is^(,(,(,. P. Choffat, in Heim's Mech. Geb. 



flexure-fault. Fig. 342 has a still greater displacement along the plane 

 between the anticline and syncline, with a complete separation of the 

 originally continuous beds, as the numbers on them show. This thinning 



and faulting are due to the friction 

 342. between the overlying and underlying 



flexures during the overthrust move- 

 ment. The facts teach that a regular 

 unfaulted overturn flexure, like that 

 represented in the part to the right 

 of Fig. 91 (6), on page 103, is only an 

 ideal form. 



The Alps had been the scene of 

 earlier mountain-making after both the Archsean and Carbonic eras. 

 The chain of the Alps includes, therefore, (1) Archaean, (2), post-Carbonic, 

 (3) post-Miocene ranges ; and the Juras belong with the last in time. 

 The proof that an upturning took place after the Carboniferous or Permian 

 is shown in Fig. 340 ; the Jurassic beds (which include, at bottom, the Lias) 

 rest unconformably on the Carboniferous, evincing that a time of upturning 

 had intervened. In the Oriental Alps, the great upturning was post-Cre- 

 taceous instead of post-Miocene. 



A flexure-fault from the Alps. Helm. 



343. 



Post-Nuramulitic upturning in the Himalayas. La Fouche. 



2. Post-Nummulitic upturning in the Himalayan Range. — In the Upper 

 Indus Valley, Middle Tibet, in the district of Zanskar, south of the Indus, 

 Nummulitic limestone (Eocene Tertiary) constitutes the summit of a peak 

 of the Singala, having a height of 19,000 feet. In the section (Fig. 343) 

 the blocked area is the Nummulitic limestone, a blackish fetid rock ; the 



