134 GRIESBACH : GEOLOGY OF THE CENTRAL HIMALAYAS. 



This section is in descending order 



Possibly 

 Upper Tithon 

 and Lowest 

 Cretaceous. 



Middle and 



Upper 



Jurassic. 



Greenisb>brown sandstone, with shales of considerable thick- 

 ness, not less than 1,200'. They form high cliffs of somewhat 

 irregular contour and a shallow synclinal, dipping about 

 20to25° inwards. They rest conformably on the beds below, 

 the passage from which is gradual. 



Friable black, to dark grey shales with concretions, yielding 

 many ' Spiti ' fossils. I could not estimate the thickness 

 owing to the rolling dip, but they rest apparently conformable 

 on the beds below. 



Gritty Crinoid limestone with many fossils, all of which are 

 very small. Pecten sp., &c. 

 Lias. Dark shaly beds of irregular thickness, oolitic in structure and 



containing many fossils, though mostly in bad preservation. 

 Mostly Cephalopods of liassic type. 



Limestone, thin-bedded, filled with Crinoid remains, and yield- 

 ing numerous fossils of upper rhaetic (Koessen) type. 



Uneven bedded, hard Crinoid limestone, grey, of considerable 

 thickness, with parting of earthy limestone yielding Koessen 

 fossils. 

 Upper About 20' of flaggy dark grey limestone. 



Rhaetic. Grey papery shales, with numerous Ostrea sp. 



Flaggy grey limestone and shales with Oyster banks. 



Massive, dark grey dolomite beds, and limestone with sections 

 of Megalodon sp. seen on the weathered surfaces. 



The dark dolomites with Megalodon are the lowest beds seen in 

 this section, exposed near the rise of the deep ravine of the Shal- 

 Shal stream. The dip of the beds is here about 25 to 30 north-east, 

 forming in fact an anticlinal, through the arch of which the Shal-Shal 

 stream has eroded its deep channel. 



West and north-west of BaVa Hoti the ground is completely 

 obscured by huge masses of debris, enormous fans stretching from 

 the Silakank and Marchauk heights down towards the valley. But 

 along the routes to both passes enough of the rocks are exposed 

 below the debris where spring torrents have cut through the latter 

 to show that the dip of the section is extremely rolling and uneven, 

 and in the neighbourhood of the fault greatly crushed and disturbed. 

 Nothing but rhaetic beds, chiefly middle and upper (" Dachstein " and 

 " Koessen beds") are exposed between Bira Hoti and the Silakank, 

 whilst west of the Marchauk middle and upper trias are overlaid by 

 the lower rhaetic dolomites. 



( 134 ) 



