TERTIARY SANDSTONES, CLAYS, &C. f>9 



to the identification of the whole as one broad system of results from 

 causes or conditions appertaining to Eocene times. 



Superficial deposits. — These hardly require any special notice. Coarse 

 atmospheric, detrital accumulations predominate, and especially in the 

 Tiri valley are scarped at different levels, as if that river in its wander- 

 ings had at certain periods excavated its channel with greater rapidity 

 than at others, its power to do this being of course influenced by the 

 height o£ the river Indus. Large surfaces of the Bannu valley are 

 occupied by gray sand derived from the tertiary sandstones ; this also 

 occurs in the lower part of the bed of the Tiri Taui and in a tributary 

 nullah from the south. A well-defined series of thick stratified deposits 

 flanks the hills east and west of (Siirdag) village, and may probably form 

 part of a vast detrital talus said to flank the Suliman hills near Bannu. 

 Calcareous tufa is exceptionally rare, while alluvium proper seldom 

 exists owing to the rapid fall of the streams ; nor have the analogues of 

 c Kadirs ' been observed, but the sandy finer earthy and sometimes 

 kunkery materials occasionally assume somewhat the appearance of 

 loess, not, however, here eaten into labyrinthine ' Kudderas, ' as in the 

 Potwar plateau, Cis-Indus. 



( 173 ) 



