GEOLOGICAL DIVISIONS. 205 



from which the materials forming the sub-Himalayan hills were derived. 

 Moreover, the mountains are very much smaller than the Himalayas, 

 and the plains round them being at an altitude greater than that 

 of the Gangetic plain tend to still further diminish their relative 

 height ; hence the Siwalik hills in Baluchistan are low in proportion 

 and constitute very insignificant ranges, although the outcrop is 

 often of considerable width. Even before desert conditions had 

 set in to the same degree as at the present day, these less pro- 

 nounced differences of altitude, and the absence of any such topo- 

 graphical contrast as exists between the Himalayan highland and 

 the Gangetic plain must have favoured a more uniform distribution 

 of the products of disintegration. Thus we find strips of Siwalik 

 strata in narrow depressions between two parallel ridges of one 

 range, though the depression deserves the name of valley rather 

 than that of plain. Such an instance will be described from Tafui 

 in the detailed descriptions (page 47). 



As to the general appearance of the strata, it is not necessary 

 to give a detailed description of them, as they are quite similar in 

 appearance to those in the neighbourhood of Fishin and Quetta, 

 which have been frequently described. 1 Throughout the area 

 examined they consist of conglomerates, of friable sandstones, and of 

 clays frequently white or brightly coloured in various tints of pale 

 terra-cotta, ochre, or green. These clays often contain crystals 

 of calcite and gypsum. 



It has just been mentioned that, notwithstanding the insignificant 

 altitude of the Siwalik hills, their outcrop frequently stretches 

 across a wide extent of ground. Very often, throughout the entire 

 width of this outcrop, the beds are seen dipping constantly in the 

 same direction with a well marked dip of as much as 20 . If, then, 



1 C. L. Griesbach, Report on the Geology of the section between the Bolan Pass 

 in Baluchistan and Giriskh in Southern Afghanistan. Mem. Geol. Surv. Ind., Vol. XVIII, 

 pp. 18-21. W. T. Blanford, Geological Notes on the Hills in the neigbourhood of the 

 Sind and Punjab Frontier between Quetta and Dera Ghazi Khan. Mem. Geol. Surv. Ind., 

 Vol. XX, p. 180. R. D. Oldham, Sub-recent and recent Deposits of the valley plains 

 of Quetta, Pishin and the Dasht-i-Beaaolat. Rec. Geol. Surv. Ind., Vol. XXV, p. 36. 



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