DELHI QUARTZITE SERIES. HI 



In the present case, on the theory adopted of the largely meta- 

 morphic character of the Aravallis, a certain 

 don. m 6XP modification of this process seems necessary 



to satisfy the facts. We must suppose that 

 the Aravallis being in part of an igneous nature and at all events 

 being much invaded by igneous material, under the consequent 

 heating and intense compression, have behaved largely like a semi- 

 solid or plastic mass. This might have allowed the quartzite 

 (whilst here and there preserving traces of stratification) to be 

 melted off, stoped away, or dissolved or pinched out down among 

 the hot and plastic Aravallis, especially towards the deeper sections 

 of the folds where their pitching axes became steepest. It may 

 even have been that some of the quartzite masses, which now 

 remain to view, were so cleaved, sheared, and finally rendered 

 plastic themselves by rock fiowage accompanied by more or less 

 free molecular motion, as to account for the blurring and effacing 

 of all traces of original bedding, such as has often been described 

 by me as characterising them. 



The case of the magnesian rocks just considered must stand by 

 itself for the present as an additional problem ; which, although 

 as yet left imperfectly explained, may on any interpretation easily 

 fit in with the general conception of the tectonic relations of the 

 Delhi Quartzite to the Aravallis outlined above. 



We may contrast this position of the Delhis here in Idai with 

 Contrast with the tne muc ^ simpler aspect of the Alwar quart- 

 position of the Alwar zite, its presumed equivalent, as described 

 qu by Mr. Heron, and which 1 can corroborate 



from personal experience. The latter is generally well bedded, and 

 the aspect of unconformity on the Aravallis is dominant ; whilst, 

 as we have seen in Idar, the relationship of the Delhis to the 

 Aravallis is more on the pattern of that of the Dharwars to the 

 underlying Archacans of southern India. 



PHYLLITE SERIES. 



On account of its conformity with, and its passage downwards 



into, the Delhi Quartzite, neither this series 

 Not a separate ,1 n iv« a_ l »i • i i 



system. nor tJti e Delhi Quartzite series has been 



elevated into a separate system, but each 

 remains subordinate to the other with winch it appears to be con- 

 nected by many features in common. In development, the Phyllite 



i2 



