CHAPTER IV. 



Met amorphic Series. 



Except towards the north, where the alluvium surrounds the sand- 

 stones, metamorphic rocks are exposed at the base of all the sections 

 which occur on the western flanks of the B-ajmehal hills. These rocks 

 consist of gneiss alternating" with micaceous and hornblendie schists. 

 The gneiss is sometimes excessively granitoid, ex- 



Foliation. 



hibiting foliation only on the large scale. This 

 character is seen in many places, but especially in some detached hills 

 which rise through the alluvium in the north-west and in the small 

 islands in the Ganges at Colgong. In the latter case the rock is very 

 massive and contains large crystals of felspar. 



Along the western frontier of the hills, these rocks, which are con- 

 nected with those occupying a large area in Bir- 

 bhum and Behar, shew a considerable amount of 

 disturbance, and numerous veins of largely crystalline felspathic granite 

 strike through and across the layers of t gneiss and schist. The dip of 

 these'rocks is tolerably persistent, being generally 

 ip ' more or less to west of north at angles varying 



from 40° up to 85°. Exceptions, however, occur locally where the dip is 

 in the opposite direction. 



The line of junction between the metamorphic and younger rocks 

 in the southern part of the area, between the 

 Boundaries. Dwarka an d Brahmini rivers, follows a pretty 



definite course, the boundary being in this portion faulted. North of 

 the Brahmini the junction becomes more irregular, and east of the 

 Mohwagarhi hill denudation has laid bare a detached area of the meta- 

 morphic rocks which is surrounded on all sides and isolated by the sedi- 

 mentary deposits. 



( 173 ) 



