DELHI QUARTZITE SERIES. 79 



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we proceed with the ordinary description of the Delhi quartzite 



areas. 



Taken as a whole the areas may be divided into two categories, 



namely: (I) a. region of broad outcrop areas 

 I wo categories. , - . " r 



which m a S.W. direction end among the 



Aravallis in a set of blnnt processes arranged one behind the other 

 en echelon, and which in the other direction coalesce, or apparently 

 coalesce, into still wider hill-masses across the border, outside Jdar 

 State ; (2) a region of narrow outcrop areas, which twist about in 

 a complicated way that can only be appreciated by reference to 

 the map. The former, or broad outcrop areas, lie more to the 

 north-west, and the latter, or narrow outcrop areas, to the south- 

 east as a whole ; and it seems likely, on a priori grounds, that the 

 former are connected with a. more expanded free surface of them 

 exposed to view by denudation, whilst the narrower areas depend 

 for their limited breadth on the fact that the superposed phyllite 

 series just there has not yet been sufficiently removed by denuda- 

 tion. A very similar arrangement into broad and narrow areas 

 appears to be reflected in the disposition of the Alwar quartzite 

 in the region recently described by Mr. Heron. 



At the northern end of our area, in the neighbourhood of the 

 Ilarnav river and as far south as Chorivad 

 Chorivad! tllc ^ cmi quartzite builds the usual promi- 



nent ridge, generally speaking, though some- 

 what dissected by side streams in its more northerly part. 

 Actual observations of the rock were made at the following 

 localities: (1) the 1.150 feet hill-spur and neighbourhood, I. 1 , miles 

 E.N.E. of Walren. (2) in the Ilarnav river-bed. (3) south of 

 Kalol, and (4) along the straight ridge north of Chorivad. The 

 exposures at locality (1). near AValren and at Derol, where the 

 remarkable stoped contacts with the biotite-gneiss occur, have 

 been described when treating of the latter (see p. 25). It is 

 only necessary to add that there are occasional thinner-bedded 

 schists intercalated among the ordinary quartzites of the 1.150 

 feet hill and neighbourhood. Near Talao and at a point about north 

 of hill 1150 a small road-cutting exposes a few white aplite veins 

 with tourmaline, which arc intrusive in the quartzite. There are 

 also white quartz veins. No good dips are visible, excepting at 

 the summit where dips of 30° and 40° E.N.E. are illustrated by 

 a good banding of vein quartz and a tendency to split, until 3 or 



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