66 



GR1ESBACH: GEOLOGY OF THE CENTRAL HIMALAYAS- 



following deposits. This line could nowhere be drawn, except at 

 the unconformity between the carboniferous and the Productus 

 shales; from the latter deposits to the liassic limestones above it is 

 one unbroken chain of deposits, passing one into the other by gradual 

 lithological changes. 



Considered from both a lithological and palaeontological point of 

 view, this group of strata may be divided into the following systems 

 or divisions in descending order: — 



Numbers in 



figured 



seciions. 



16 



Divisions. 



Systems. 



,ias. 



15 



14 



Lithodendron limestcne 

 Dolomites . 



13 

 12 

 II 

 10 



Modiola beds 

 Daonella ,, 

 Ptychites Gerardi zone 

 Otoceras „ 



Productus shales 



Rhaetic. 



Upper 



Lower 



Trias. 



Permian. 



5. Permian , Productus shales (9). 



At once almost the most insignificant in thickness and the most 

 easily recognized lithologically, this horizon forms one of the most 

 important landmarks in the structure of the Central Himalayas. Gen- 

 erally resting on the white quartzite (8) of the upper carboniferous it 

 sharply contrasts with the latter ; consists of very dark, occasionally 

 micaceous shales, exceedingly friable and crumbling into an earthy dark 

 mass. The shales may be said to be carbonaceous here and there, with 

 coaly traces, — carbonized vegetable matter. A few irregular partings 

 of hard ferruginous sandstone divide the thickness of shales ; an occa- 

 sional string of nodular clay iron ore is found in place of such sand- 

 stone partings. In lithological character these shales differ so little 

 from the next higher horizon, that it is easy to mistake one for the 

 other. The higher Otoceras beds are, however, less earthy and not 

 ( 66 ) 



