144 GEOLOGY OF THE SON VALLEY, ETC. 



_, bluish and weathering light yellowish brown. 



The ■ Trappcid " rock. 



Quartz-grains, mostly rounded, with sparsely 

 distributed felspar crystals, make up the rock. These hard, coarse 

 beds do not occur entirely and purely by themselves, but often have 

 finer-grained shales interbedded with them. Following the Porcel. 

 lanics down the Nagour, these harder beds are first met with just at 

 its confluence with the Son and can be well followed up the Son 

 along its left bank, until finer porcellanic shales forming the lowest 

 beds of the stage are come upon again. These harder beds are 

 difficult to map, as they do not form a pure band by themselves nor 

 keep to the same position, but are, on the other hand, very inconstant 

 and variable. They are, however, more or less traceable all the way 

 from Baikona to Marjatpur and from Marjatpur by Amlai to Garhara. 

 Between Garhara and the Son one does not see much of the rocks 

 owing to the preponderance of alluvium. 



By Jhinna and Marjatpur a thin band of limestone occurs towards 



Limestone interbedded the u PP er P arts of the Porcellanics, intercalated 

 in the Porcellanics. ^'^ the typical porcellanic shales, effervescing 

 freely with acids. This limestone passes gradually and impercepti- 

 bly into the shales above and below, the passage rock effervescing 

 less and less until the bluish rock into which the limestone eventually 

 passes does not at all effervesce with acids and seems entirely free 

 from calcareous matter, though in look and appearance it would be 

 the easiest thing for anybody to mistake it for a limestone. 



III.— Kheinjua Stage. 

 Overlying the Porcellanics there occurs a mass of alternating 

 shales and sandstones with occasional bands of 



Kheinjua beds. 



limestone. These shales and sandstones, though 

 they naturally vary somewhat as they are traced from the base 

 upwards, still, taken together, present a relationship and unity of 

 character to entitle them to rank as of one group or stage, and this 



including all the beds from the upper boundary 



Their position defined. 



of the Porcellanics as far as the commencement 

 ( M4 ) 





