C. A. Cotton—Block Mountains in New Zealand. 283 



about 20 feet per mile, but it is still in the narrow-floored, rock- 

 walled Taieri Gorge (%. 22), which is incised at one place to 

 a depth of abont 1,000 feet below the plateau surface. 



The Shag Yallej fault angle is drained by the Shag River, 

 which rises in the maturely dissected uplands overlooking the 

 Maniototo Plain and follows the line of the depression in a 

 northeasterly consequent course to the sea. 



Most^ of the tributaries of the streams in the Central Otago 

 depressions flowing over the rocks of the undermass might be 



Fig. 22. 



Fig. 22. View looking down the Taieri Eiver at the upper end of the great 

 gorge in which it traverses the Bare wood Plateau. 



considered superposed consequents instead of normal conse- 

 quents, if it can be shown that their directions were determined 

 by the slope of a former cover. They are indifferent to both 

 the dip and the strike of the underlying rocks, but as they 

 follow the slope of the surface of the undermass they may be 

 classed as simply consequent, whether they were initially 

 guided by the slope of the planed and tilted surface now visible 

 or by the slope of an overraass for which that surface formed 

 a floor. 



A distinctly different kind of superposition is shown by the 

 Manuherikia River and the Ida Burn, flowing parallel with the 

 tilted Raggedy-Blackstone and Rough Ridge blocks, and also 



