286 G. A. Cotton — Block Mountains in New Zealand. 



erii boundary of the block-complex with predominating north- 

 westerly trend which forms the northern highland of Otago, 

 In the Middle Waitaki graben there are a number of small 

 blocks in various attitudes. On the northern or Canterbury 

 side of the graben the dislocations seem to belong to the north- 

 easterly system, though trending somewhat irregularly, while 

 farther north the highest blocks are elongated generally in a 

 north-and-south direction. 



One great depression, occupied by the consequent course of 

 the Hakataramea Riyer, a tributary of the Waitaki, is of great 

 length and has a width on the floor of about Ave miles. It is 

 bounded on the west by an imposing fault scarp of the block 

 forming the Kirkliston Range, 6,000 feet high ; but its chief 

 peculiarity is a bar of the undermass about half a mile wide and 

 rising about 400 feet aboye the leyel of the riyer, which forms 

 a kind of sill across the outlet, cutting off the excayated low- 

 land within from the Waitaki depression and riyer. The sill 

 is trayersed by a narrow, rock-walled gorge cut by the outflow- 

 ing Hakataramea Riyer. A layer of bedded fluyiatile gravel 

 on the top of the sill proyes that the great lowland of the 

 Hakataramea Yalley upstream from the sill has been eroded by 

 the riyer during the time occupied in cutting the outlet gorge 

 through the sill. A number of terraces in the depression 

 mark stages in the excavation of the lowland. In the earliest 

 postdeformational cycle, the undermass of the sill of the Haka- 

 taramea depression had probably not been revealed by erosion. 



5. The Surfaces of UpUfted Blocks. 



StrijpiKd Plateau Surfaces. — With the exception of the lava- 

 protected areas, the cover has been stripped from the uplifted 

 block surfaces. The only indication of its former existence 

 is the occurrence of " sarsen stones." The planed surface of 

 the undermass is thus revealed, and in a few places subma- 

 turely or maturely dissected. 



The stripped plateau surface survives over large areas, even 

 on slopes exceeding 10°. The precipitation is small and the slopes 

 are drained by systems of numerous, intermittent, parallel con- 

 sequent streams and a few unimportant insequents ; but no 

 distinctly subsequent streams or positive relief forms on the 

 surface of the undermass have been observed. The edges of 

 the interfluves are almost invariably rounded by soil creep. 



The type of stripped sloping-plateau surface with very shal- 

 low dissection is of general occurrence in Central Otago and 

 the neighboring area to the northeast. (See figs. 2, 3, 17.) 

 This type of surface appears to have a close analogue in that 

 found on the flanks of the resequent or stripped anticlinal 



