THE COUNTRY EAbT, ETC. 16/ 



invoking the aid of faults which cannot be traced in the main bound- 

 ary of the lower Vindhyans. 



This area is remarkable, as containing the only known case of 

 intrusion of an igneous rock in the lower Vin- 



igneous intrusion. dhyans> In t h e stream-bed close to the village 



of Pataudh (Putwud), a dyke is exposed cutting the shales of the 

 lower portion of the Kheinjua stage. Two others were seen on the 

 track between Pataudh and Kanch (Kunuch). In each case the 

 rock is very much weathered and has a soft ochreous and buff 

 coloured weathered coating ; with some trouble I was able, after 

 breaking through this, to get some fragments of small cores of a 

 comparatively unweathered grey rock, specific gravity 2-85, showing 

 numerous small granules on the fractured surface. Under the 

 microscope the rock consists of a ground mass of interlacing crystals, 

 decomposed beyond possibility of recognition, while the granules are 

 seen to be colourless almost spherical casts, lined with quartz crystals 

 and not infrequently containing a few grains of an opaque min- 

 eral. Many of these, where they have been cut nearly through the 

 centre, show a distinct approach to a hexagonal outline with rounded 

 corners, resembling sections of leucite crystals. The rock appears 

 to be, in fact, a much decomposed leucite rock. 



The age of this intrusion cannot be fixed. It is certainly later 

 than the outbursts which formed the ashes of the porcellanite stage, 

 but how much later it is impossible to say. 



In the limestone exposure at Markundi there are some curious 

 dykes of sandstone, one of which is represented 

 on Plate 2. They cut across the bedding, and 

 ramify in a manner which simulates an igneous intrusion, but the 

 rock which fills their veins is a sandstone composed of rounded grains 

 of sand, cemented by a calcareous cement. In places this gives way 

 to a limestone breccia, and fragments of limestone are not uncom- 

 mon in the marginal part of the dykes. Similar dykes have been 

 described by Darwin. 1 Diller, 2 Gresley, 3 and other observers, and 



, l Naturalist's Voyage round the world. 



3 J. S. Diller, Sandstone dikes. Bull. Geol. Soc. Am. I, 411 — 441 (1890). 

 8 W. S. Gresley, Clay veins vertically intersecting coal measures. Bull. Geol. Soc, 

 Am. II, 35-58 (1808). 



( 1^7 ) 



