THE PATLI DUN. 63 



Fi . 1. Fig. 2. 



They resemble a gigantic staircase that has suffered some con- 

 vulsion of nature. Beyond the Sona N. in a N.N.E. direction the 

 river shows no exposures for some way, and widens out into the allu- 

 vial flats which form the western termination of the dun. Near Boksa*r, 

 however, low cliffs washed by the river still give exposures of the 

 sand-rock, but the dip is more nearly due north than before at a uni- 

 form angle of 20 . Suddenly, nearly a mile N.N.W. of Boksar, they 

 cease altogether, a fault intervenes between them and the Siwalik con- 

 glomerate, and we then enter upon one of the most striking features 

 in the structural geology of the Sub-Himalaya. The fault, however, 

 between the conglomerate and the sand-rock is probably of no great 

 throw in relation to others that we are about to examine, and has 

 taken place along a synclinal bend. It has been sufficient, however, 

 to cause the thin band of conglomerate to vanish on the south side of 

 it It is doubtless a mere local fracture and does not extend far in 

 either direction. On the north side of this fault the Siwalik conglo- 

 merate forms the north limb of a compressed synclinal fold, dipping 

 generally 50 S.S.E. Its outcrop in the river section is about half a 

 mile across, showing the attenuated condition to which it has been 

 reduced by the nipping- out process already referred to, though, as 

 will be shewn later on, the conglomerate was probably never very 

 thick west of the Pa*tli dun. The northern boundary of the con- 

 glomerate is a reversed fault, near which the previously mentioned 



( 121 ) 



