Chap. I] general description of rocks. 13 



the Kasaoli beds indicates the continuance of peculiarly tranquil con- 

 ditions, contrasting, as will be seen, with the phenomena of the suc- 

 ceeding groups. There is perhaps now an over-tendency to allow fossil 

 evidence too exclusively to regulate our classification of rock series. 

 Should the fossil evidence here require a great lapse of time, and con- 

 sequent sub-division of the series, while accepting these additional 

 facts and their consequences, let us not on that account destroy the 

 independent unity of the whole. 

 The rest of the Sub-Himalayan rocks might, from some general consi- 

 derations, be regarded as but one group. Although 

 Nahun group. 



the accumulated thickness would thus be enormous, 



there is much greater sameness of composition throughout than I have 

 described in the Subathu group. The structural character and compo- 

 sition of the Sivalik rocks, already so well marked in the Dugshai and 

 Kasaoli beds, continued without exception through all the succeeding 

 deposits. But we can distinguish at least one interruption to the process of 

 deposition, resulting in well-marked and general unconformity. The 

 groups, thus separated, I will distinguish as the Nahun group, and 

 the Sivalik group, or as the middle and the upper groups of the Sub- 

 Himalayan series. It will be seen on the map that the junction of the 

 Nahun group with the rocks on the south is very irregular : it is, 

 however, a very decided boundary, and can be followed with the utmost 

 precision through this region of continuous hills between the Kyarda 

 and Pinjor duns. In the duns this junction is almost always concealed 

 under the talus of the inner slopes. There is no better section of it 

 than at a point three miles south of Nahun, in the valley of the Mar- 

 kunda ; plate I. is a view of this junction, taken from the bed of the river, 

 a few yards to the south. We find there regular beds of unconsolidated, 

 brown, earthy conglomerates, and brown clays, dipping steadily at a 

 moderate angle against the crushed, upturned, lower beds of the Nahun 

 group, in which clays of a clear bright red are conspicuous. The 



