274 C, A. Cotton — Block Mountains in New Zealand. 



Blackstone Hill. The back slope has an inclination of about 10° 

 towards the northwest, where the stripped surface of tlie under- 

 mass passes under the covering strata of the Manuherikia de- 

 pression. The southeastern face, or front, of the block is a 

 fault scarp (tig. 15) against which are upturned the covering 

 strata in the next depression. 



This depression, known as Ida Yallev, is traversed bj the 

 Ida Burn and Fool Burn. The mean height of its floor above 



Fig. 14. 



^m^^ ^^^^m 



Fig. 14. View looking westward across the Maniiherikia depression from 

 the back slope oi" the Raggedy- Blackstone block. The southern end of the 

 Dunstau block is seen in the distance and the valley of the Manuherikia River 

 in the foreground. 



the sea is about 1,500 feet. It is abont 25 miles long and 3 or 

 4 miles wide and has the same northeast and southwest trend as 

 the associated blocks. It is floored largely by postdeforma- 

 tional alluvium, but the covering strata appear at a few pohits 

 along the margins. At the southwestern end the stripped 

 floor appears and rises to merge with the upland plateau. 



To the east another upland block forms Rough Ridge. Its 

 crest is very even for many miles with a height of about 3,200 

 feet above the sea. On its northwestern and northeastern 

 sides this block is similar to the Raggedy-Blackstone block. 



