3° GEOLOGY OF THE SON VALLEY, ETC. 



the boundary takes a southward turn and, for a while, is irregular 

 in form, ceases to show any sign of faulting, and becomes a natural 

 boundary along which the sandstones of the upper Gondwanas rest 

 in unconformable contact on the crystalline rocks. After the south- 

 ern trend the boundary once more becomes a faulted one, continuing 

 so to near the Gopat, where for a short distance it seems to become 

 normal once more, but shortly after crossing the Gopat resumes 

 its faulted condition, which it maintains to near the limit of the 

 map. Near and beyond this the boundary once more becomes one 

 of unconformable superposition. 



The detailed examination of the Gondwana boundary has been 

 of interest, as it was in this area, though further to the west, that 

 Mr. Medlicott arrived at the conclusion that the apparently faulted 

 boundaries were in reality due to the accumulation of the Gondwanas 

 against inland cliffs. This opinion led to two very divergent views 

 of the original extent of the Gondwana deposits : one school regard- 

 ing the present limits as due to the removal by denudation of the 

 upheaved portion of the beds, the other regarding the original extent 

 of the formation as very much the same as its present distribution, 

 and considering that the supposed faulted boundaries were an error 

 of interpretation. 1 



The differences have been completely reconciled during the 

 recent survey and the true nature of the boundary been elucidated; 

 this finds its most complete and explicit expression in the section 

 east of the Gopat, carefully examined by Mr. Vredenburg, whose 

 description will be found in Chapter VIII. 



Put briefly, it may be stated that the Gondwana beds were 

 deposited against inland cliffs, but these cliffs 



Contemporaneous faults. 



were iault clins, that is to say, they were the 

 result of an immediately preceding movement along fault planes, 

 which movement resulted in a decided inequality of the surface. The 

 faults to which these cliffs owed their origin were not, however, 

 wholly antecedent to the formation of the Gondwanas. Movement 

 took place along them during the Gondwana period, and so it results 

 1 Manual, ist Ed., Vol. L, p. 103; 2nd Ed., p. 154. 



( 30 ) 



