COUNTRY NORTH OF THE SON. 125 



Chapter VIII.— COUNTRY NORTH OF THE SON 

 BETWEEN LONG. 82 AND 82 30' E. 

 (R. D. Oldham.) 



In the main area of lower Vindhyans the lower stages of the 



Lower Vindhyan series are exposed with a somewhat compli- 



mamarea. cated structure, being thrown into numerous 



folds and cut by many faults. There are two inliers of gneiss in 

 this area. 



The basement beds in the country north of Khaira were found 

 by Mr. Grimes to be penetrated by quartz-veins which pass down- 

 wards into the granite. These veins must, however, be of later date 

 than the majority of the quartz-veins which are found in the crys- 

 talline area and are in many places truncated by the surface of 

 unconformable contact at the base of the lower Vindhyans. 



In this same area a conglomeratic band is found at the base of 

 the porcellanite stage, the pebbles consisting of a green fine-grained 

 rock, undistinguishable from similar beds which are found interstrati- 

 fied in this stage. The great expanse of rocks of this stage to the 

 south of Sahaol is partly accounted for by repetition through folding ; 

 there can, however, be little doubt that north of latitude 24 30' 

 Mr. Datta has included a greater thickness of strata in this stage than 

 was done by Mr. Grimes and myself in the country to the south. 

 There are very few exposures in the northern part of the area coloured 

 as porcellanite, and the northern boundary is based on two isolated 

 exposures in the Son, which may either be inliers of the rocks 

 included, to the south, in the porcellanite stage, or more probably 

 stray beds of a similar rock in the Kheinjuas. 



At the eastern end of the area, along the 83 meridian, these 

 beds have thinned out and at the same time become much less 

 characteristic. 



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