UPPER TEIAS OF BYANS. 
This decrease of the carnic stage from N. W. to S. E. is intimately 
coiiiiected with a cliangc of fades. The shaly deposits of the horizon 
of Ilalobia coinala in the Bambanag section are replaced in Byans by 
pure grey limestones, in which no trace of shaly layers has been found. 
It would be an interesting task to search for the connecting links 
between the different facies of the two areas, which must pass into one 
another somewhere between Johar and Byans. 
The rich fauna of the Tropites limestone showing an assemblage of 
carnic and noric elements, all the higher beds following above, must be 
assigned to the noric stage. 
In the district to the north of the Kali and Kuti Yangti rivers A. v. 
Krafft distinguishes the following sequence of beds above the Tropites 
limestone : — 
4. Series of limestones (not examined in detail). 
3. Shales with undeterminable ammonites. 
'2. Grey limestone of great thickness. 
I. Black shales with Arcestes sp. : about 1,000 feet. 
F. H. Smith in his generalized section of the Triassic rocks observed 
in Byans, distinguishes a larger number of rock-groups, according to 
the colours of the blue-grey limestone exhibited on weathered surfaces. 
But, broadly speaking, two main divisions can be recognised, a lower con- 
sisting of dark shales, and an upper, about 1,500 feet in thickness, in 
which limestones predominate. The shaly band No. 3 has been 
observed in the section of Kalapani only, where it is strongly crushed. 
The occurrence of shaly deposits, 1,000 feet thick, in the lower divi- 
sion of the noric stage, once more emphasizes the dissimilarity of the 
Upper Triassic beds developed in Byans to those of Johar and Spiti. 
On the other hand the upper division of the noric (rliaetic ?) beds of 
Byans seems to agree with that of the districts described above, consist- 
ing, as it does, of a thick limestone series extending from the Upper 
Trias into the Jurassic system and overlain by the Upper Jurassic Spiti 
shales. As is evident fron F. H. Smith's notes, the ferruginous oolites of 
the Sulcacutus beds form a constant and well marked horizon on the 
top of the limestone series No. 4 both here as v/ell as in the more 
north-westerly districts. 
( 320 ) 
