172 KRAFFT: EXOTIC BLOCKS OF MAILA JOHAR. 



In his description of the carboniferous volcanic rocks of the Firth 

 of Forth basin Sir A. Geikie * remarks : " In a great many cases the 

 fragments of shale, sandstone and other sedimentary strata imbedded 

 in the ejected debris are so unchanged that they cannot on a fresh 

 fracture be distinguished from the parent beds at a short distance 

 from the vent. The Spirifers, Lingular Cricoids, Cyprid-czses, 

 Ganoid scales and other fossils are often as fresh and perfect in the 

 fragments of rock imbedded in tuff as they are in the rock in situ." 

 Indeed in most of the occurrences compared above with the volcanics 

 of Johar, determinable fossils have been found. 



The absence of contact minerals is a still less conclusive objection: 

 Diener himself describes Peak Chirchun No. i as being traversed by a 

 dyke and yet no contact minerals were found. Nor have I discovered 

 any near the intrusive veins so often met with in exotic limestone 

 blocks. If then they were not produced by these intrusions, there is 

 no necessity why they should be present at all. 



But there is another more powerful objection that might be raised 

 to the theory advanced above. 



We have so far not taken into account those huge, grey limestone 

 masses, found within the Kiogarh high plateau and the large masses 

 of Gieumal sandstone occurring in the Balchdhura heights. The size 

 of these blocks is so stupendous, that the impossibility of their being 

 ejected through volcanic vents might be urged. I am unfortunately 

 not in possession of exact data as to the volume of the largest blocks, 

 yet there can be little doubt that some of them are many thousand 

 cubic yards in bulk. To bring up such enormous masses, eruptive 

 forces are required infinitely more violent than those to which the 

 non-volcanic fragmental materials of Mount Vesuvius or the Eifel are 

 due, and yet this is, in my opinion, the only possible explanation. 3 We 



1 Transactions Roy. Soc, Edinburgh, Vol. XXIX, 1880, p. 459. 



2 There can be no questicn of the large blocks being in origin essentially 

 different from the smaller ones. The limestone fragments met with are of all sizes 

 from small pieces up to huge blocks, the two extremes being linked by every 

 possible intermediate size. On the whole, the higher we ascend in the volcanics, 

 the larger the blocks, but also the largest ones are surrounded and partly covered 

 by igneous rocks, in which small sized limestone fragmenfs occur. 



( 45 ) 



