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



from the northwest emerges from the fault angle between the 

 Dunstan and St. Bathans blocks. These streams are fed by a 

 large number of small tributaries which with the exception of 

 the Fool Burn are consequent on the slopes of the neighbor- 

 ing block mountains. 



The Pool Burn, which enters the Manuherikia depression 

 from the southeast, cuts transversely across the narrow Bag- 

 gedy-Blackstone block in a deep gorge. This transverse course 



Fig 20. 



C.a.c.rtov,..l<=>LS. 



Fig. 20. Maturely dissected fault scarp of the Kakanui block, 

 ing north across the eastern margin of the Maniototo depression. 



View look- 



has been described by Park as a capture (1906, p. 13), but none 

 of the features generally associated with recently effected cap- 

 tures are to be seen in the valley system. Neither of the 

 longitudinal streams of the Ida depression-the Pool Burn and 

 the Ida Burn-which unite to flow through the gorge, can have 

 been reversed by capture unless the capture took place before 

 the excavation of the covering strata. 



Park says, "The Ida Yalley basin, as shown by the river 

 terraces and surface contours, at one time drained into the 

 Maniototo Basin." He describes the Ida Burn for a distance 

 of over 12 miles as a reversed stream; but in that distance it 

 has a fall of 500 feet, and it flows the whole distance in a flat- 

 floored valley opened to the full width of the Ida tectonic 

 depression. Such terraces as survive descend in the same direc- 

 tion, giving no indication of reversal. There is, moreover, 

 no stream nor abandoned valley of erosion that can be inter- 

 preted as the beheaded former course of the Pool Burn. 

 Furthermore, it is difficult to explain why a tributary of the 

 Manuherikia should breach the Baggedy block. The climate 



