40 



IIAYDEN : GEOLOGY OF NORTHERN AFGHANISTAN. 



nothing to distinguish it from the recent deposits of similar composi- 

 tion. 



In the Gandamak plain there are several small hills made up of 

 piles of enormous blocks of crystalline limestone, quartzite, granite and 

 igneous rocks all jumbled together. The limestone blocks are espe- 

 cially large — up to 10 feet or 12 feet in diameter ; other blocks are 

 smaller, but often three, four and five feet in diameter. Whence and 

 how these blocks came here it is difficult to guess, but their size suggests 

 ice as the transporting agency. I only saw them in the immediate 

 neighbourhood of Gandamak and they appear to be quite local. Rocks 

 like them occur in situ in the Siah Koh, but if they were brought to 

 Gandamak by ice, one would be more inclined to look for the parent 

 mass in the Safed Koh to the south. 



Beautifully striated pebbles are found throughout the sandy plain 

 between Jalalabad and Baoli ; these might easily be taken for glaciated 

 pebbles were they not also pitted in the manner so characteristic of sand- 

 sculpture ; as they occur und'3r desert conditions, I have no hesitation 

 in attributing their sculpture to wind rather than to ice. The pebbles 

 are derived from the Siwalik conglomerates and occur now among the 

 recent plain deposits ; they are only referred to here in view of the fact 

 that their sculpture might be attributed to post-pliocene glaciation 

 and the deposit in which they occur be thus erroneously regarded as 

 pleistocene. 



Ill DESCRIPTIVE. 



The Kabul river=valley below Jalalabad. 



From Jalalabad, until it plunges into the precipitous gorges below 

 Lalpura, the Kabul river runs through an alluvial valley, usually broad 

 and open but occasionally closed in by the approach of the hills on 

 either side. Here and there small hillocks and ridges rise up through 

 the alluvium. On either side of the valley huge talus fans from the 

 Safed Koh on the south and from the ranges of Kunar and the 

 Mohmand country on the north, slope down to the river. Throughout 



