STRATIGRAPHICAL ELEMENTS : JURASSIC. 33 



In the Sha-ala-ditta neighbourhood there are deposits of brown 

 rusty-coloured sandy limestones, or calcareous sandstones, which are 

 crowded with compacted trigoniae. These beds stretch away west 

 and south-west of the Hazara boundary, and are well developed 

 at the Margalla pass. In these southern localities, on account of 

 the absence of the Spiti shales, it is sometimes difficult to fix the 

 boundary between the Triassic and the Jurassic series. 



For a long time I was completely baffled in trying to determine 

 the relative position of the southern type of Jurassics as regards the 

 northern type. It was a point left doubtful by Mr. Wynne. 1 The 

 difficulty was that longitudinal valleys denuded along the axes of 

 flexures shewing the northern type on one side and the southern type 

 on the other prevailed throughout this part of Hazara. Passage 

 sections were, however, at last found ; and the general way in which 

 the one type dovetails into the other will be best seen in the de- 

 scribed sections (see Nummulitic zone, Chap. IV, page 177)* 



With the Spiti shales we have arrived at a great palaeontological 

 Paleontology of the landmark. Besides their lithological identity 

 Jurassics. with those of Spiti, we have sufficient fossil 



evidence to fix their Jurassic age beyond much doubt. Dr. Waagen 2 

 wrote of the Spiti shales of Chumbi peak near Changla Gali : 

 " Here I collected— 



Oppelia acucincta, Strachey. 



Perisphinctesfrequens, Opp. Coni simplex, Sow. 



Belemnites Geradi, Opp. 



Inoceramus. 



Cucidlcea. 



Pec ten. 



all common species of the Spiti shales." In their joint memoir 

 Waagen and Wynne wrote : il The Spiti shales though not 



1 Rec. G. S. of I., Vol. XII, 1879, p. 125. 

 a Ditto, Vol. V, 1872, p. 17. 



D ( 33 ) 



