C. A. Cotton — Block Mountains in New Zealand. 289 



1908, p. 12). This reduction of the block surfaces is not the 

 result of channeling. The convexity of the edges of the inter- 

 fluvial areas indicates that soil creep plays a part; but on the 

 more nearly level interfiuves, erosion is more probably of the 

 sheet-Hood kind. 



Salients on Block .(%r/ac^,s. — Preexisting salients on a plain 

 that has been strongly and in places irregularly deformed can 

 not always be recognized with certainty even in an early stage 

 of the postdeformational cycle (p. 257), and some may have been 

 overlooked by the writer. On such of the Central Otago blocks 

 as have been evenly uplifted, however, salients are absent. 

 Mount Ida, on the edge of the northern highland, is perhaps a 

 monadnock. Park suggests that Mount St. Bathans also is a 

 monadnock rising above the level surface of the Dunstan 

 Range (Park, 1906, pp. 6 and 8), but this is a distinct block 

 (p. 278). 



On the northern end of the Eock and Pillar block and on 

 the gently tilted blocks of the eastern or Barewood Plateau are 

 small prominent salients which are probably without exception 

 lava-capped remnants of the overmass. 



Scarjjs of the Schist Blocks. — The majority of the scarps 

 following lines of dislocation in Otago are at the present stage 

 of denudation in part fault-line scarps revealed by the removal 

 of the covering strata. Since the fault scarps on the same 

 lines had not been destroyed by erosion prior to the develop- 

 ment of fault-line scarps, there is no danger of misinterpreting 

 the geologic history in considering them entirely as simple 

 fault scarps. Fault scarps form the boundaries of a number 

 of blocks in Central Otago, and sufficient evidence of faulting 

 is furnished by the attitude of the covering strata at the bases 

 of the scarps. Along the front of the Dunstan block these 

 beds are shown by Park (1890 c) and McKay (1897, figs. 20, 

 21, 26, 27) to be steeply inclined, vertical, and even overturned. 

 The dip of the schist-foliation has been shown also by Park 

 (1906) to become steep in the vicinity of the fault line, show- 

 ing that the scarp is at least at its southwestern end a composite 

 fold and reverse-fault scarp similar to that forming the south- 

 eastern slope of the Kaikoara Mountains in Marlborough (Cot- 

 ton, 1913). This block boundary is the line of the Matiuheri- 

 kia fault of McKay (1897). The evidence of compression 

 found here is in accord with what is known of the dislocations 

 farther west. 



Along the front of the Raggedy-Blackstone block the strata 

 are upturned, as shown by Park (1890 <2, p. 21), along a fault 

 termed by McKay (1897) the Blackstone Hill fault. McKay 

 writes : "This line runs nearly parallel to that along the south- 

 east base of the Dunstan Mountains, and both lines have on 

 the opposite side of the valley an outcrop of quartz drifts dip- 

 ping at a lower angle in a northwest direction, or away from 



