MECHANICS OF FORMA TION OF ARCUA TE MOUNTAINS 187 



the strong Malm of the competent arch, the anticHne is backfolded 

 and in a degree dependent upon the thickness of the weaker 

 formation. 



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Fig. 29. — Backfolding due to the presence of a disjunctive surface in the folding 

 formations. Series of profiles through the Weissenstein, Chain Jura (after Buxtorf). 



The same district of the Weissenstein folds has supplied an 

 equally instructive example of backfolding (near Balmberg- 

 Giinsberg), but one where the determining local weakness was a 

 plane of fracture and not a zone of weak rock (Fig. 29). 



