Cotton. — Block Mountains and a " FoshI " Denudation Plain. 73 



range, tiie denudation plain is completely dissected away, and only 

 fully mature forms developed in the current cycle are seen. So far as 

 the writer is aware, no reniants of tiie denudation plain or of the cover- 

 ing strata are preserved on the higher parts of this range. There can 

 be little doubt, however, as to the general truth of the foregoing explana- 

 tion of Mount Perry and neighbouring peaks — namely, that they have 

 been carved by erosion, in the cycle still current there, from an upfolded 

 mass of the older rocks, the upper surface of which was, in all pro- 

 bability, prior to the deformation, a denudation plain continuous with 

 that preserved on the Gouland Downs, and carried, like it, a cover of 

 younger strata. Several miles farther south, however, where the same 

 range still forms the boundai-y of the " downs," the fold structure of 

 the mountain-flank may be replaced by a fault; but as the range is there 

 composed of granite which is somewhat easily decomposed, and as the 

 slopes are forest-clad, the interpretation of the scarp is not a simple 

 matter. 



A "Catenary" Saddle. 



The southward-facing scarjo of the Slate Range was referred to above 

 as forming the northern boundary of the plateau-floor of the Gouland 

 Downs. As the floor rises towards the east, however, its level approaches 

 that of the crest of the Slate Range, the scarp of the latter diminishing 

 in height and finally dying away. The north-eastern part of the 

 " downs " surface w^ould apparently be continuous, therefore, with that 



saddle. Mount Perry is on the right, and the Wakamarama fault-scarp in the 

 Angle of view, about 75°. 



of the summit of the range were it not for the fact that it is separated 

 from it by a deeply eroded gorge — that of the Big River. In the neigh- 

 bourhood of this gorge dissection of the surface is naturally in a some- 

 what advanced stage, but there is still an accordance of the levels of 

 the interfluves indicating the initial shape of the warped denudation 

 plain. In this — north-easterly — direction the Gouland Downs surface 

 rises gradually to the saddle which separates the Gouland depression from 

 the Aorere Valley. 



