G. A. Cotton— Block Mountains in New Zealand. 261 



by faults or steep monoclinal flexures; when the crest line' is 

 some distance back, the descent is formed either by a fold sur- 

 face alone or by a fold surface broken by one or more faults. 



To the former class belong the fronts of simply tilted block 

 mountains. They are dissected by consequent ravines wliich 

 in the stage of early youth divide a scarp into sections and 

 later reduce it to a linear series of triangular facets. 



Fig. 6. 



Fig. 6, Dissection of a gently sloping block surface (with a cover over- 

 lying a planed undermass) by extended consequent streams from a biglier 

 block behind it. The counterpart of this surface is formed in the Aorere 

 fault-angle depression in northern Nelson. 



Davis (1912 ; 1913) has distinguished fault-line scarps of 

 generally similar form to dissected fault scarps, but originating 

 as a result of the removal of weak rocks from one side of a 

 fault which has brought weak and resistant rocks in contact. 



Composite Fault Scarps. — In JSTew Zealand many more or 

 less dissected scarps occur, which agree in general form with 

 either fault scarps or fault-line scarps, which may be in their 



