228 GR1ESBACH : GEOLOGY OF THE CENTRAL HIMALAYAS. 



epochs to the present ; indeed, the natural forces exerted on the 

 surface of our globe condition this. But in addition to this, periodi- 

 cal greater changes have taken place and are proved by the sections 

 of the Central Himalayas. 



After the lower haimanta recession of deposits from the entire 

 Himalayan area into well-defined northern and southern regions of 

 formations, we find an undisturbed sequence of beds till the upper 

 carboniferous, when clear evidences of a great overlap may be ob- 

 served. This is well marked in the Central Himalayas and is clearly 

 proved in the Per so Afghan area, where carboniferous marine lime- 

 stones are followed by littoral deposits, the upper beds of which 

 contain a triassic fauna. Here we have therefore a period of sub- 

 aerial and marine erosion of the carboniferous followed by an overlap 

 of probably a permian and triassic sequence of deposits. 



The third period of disturbance seems to belong to the lower 

 Jurassic age, where a gap (partial or otherwise) between lower lias 

 and middle or upper jurassics is probable. 



I may mention that this gap is not observable in the Perso-Afghdn 

 region, where the passage from the trias into jurassics and neocomian 



is gradual. 



On the other hand, a decided overlap on an immense scale has 

 occurred in later cretaceous times in Central Asia, and we find that 

 hippuritic limestone covers both jurassics and neocomian unconform- 

 ably. Such is less apparent in the Central Himalayas, though 

 probable enough when considering the sudden change from the sand- 

 stone and shales of the lower cretaceous to the hard, white and grey 

 limestone of the upper cretaceous. 



The fifth period of disturbance which is clearly shown in the 

 Central Himalayas occurred after the deposition of the sandstones 

 which overlie the nummulitics of Hundes and which are probably of 

 miocene age. A considerable gap seems to exist between the latter 

 and the ossiferous younger tertiaries which fill the Hundes basin. 



There is clear evidence therefore of very early disturbances having 

 taken place in the Himalayan area. There are abundant proofs that 

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