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the small fans, alluvial slopes, and flood-plains of the minor streams seems 

 inadvisable, since, according to the present writer's interpretation of the 

 physiographic history, a great space of time and two diastrophic move- 

 ments separated the building of the two groups of deposits. The super- 

 position of the coastal plain on the river-fans is, however, a conclusion 

 founded on facts, which are as follows : — 



The exposed surface of the upper part of the Ohau fan surmounts the 

 right bank of the trench in which the river now flows, and extends to the 

 line of Queen Street, which runs east from the town of Levin. Northward 

 of this line a continuous sandstone landscape stretches away in the 

 direction of Shannon, and is traversed by the flood-plain of the Koputa- 

 roa Stream, a tributary of the Manawatu Eiver. Two miles and three- 

 quarters north-west of Queen Street an artesian well was sunk in the 

 Koputaroa flood-plain to a depth of 90 ft., and the beds pierced were 

 approximately as follows : — 



Yellow clay 



Gravel 



Blue clay 



Sand 



Blue swamp-clay with wood 



Shingle with seam of clav 



9 ft. 

 10 ft. 



3 ft. 

 56 ft. 



4 ft. 

 8 ft. 



[ Alluvium of Koputaroa 

 I Stream (flood-plain). 



Sandstone formation. 



Ohau fan. 



As the site of this well is 58 ft. above sea-level, the surface of the Ohau 

 fan at this point is 24 ft. below sea-level, a level which corresponds very 

 exactly with the produced slope of the exposed surface of the fan between 

 the line of Queen Street and the fan-apex. The interfingering of fan gravels 

 and sandstone formation over a zone nearly three miles in width is in the 

 highest degree improbable, so the superposition of the sandstone on the 

 fan, and not the reverse, is thus established. 



Similar relationships are revealed in the present valley of the Ohau 

 River at a point two mfles and a half up-stream from the Wellington- 

 Manawatu Eailway bridge. A river-cliif section shows the surface of the 

 Ohau fan surmounted by a thick undisturbed layer of sandstone, which 

 has been preserved in this site by overlying gravels derived from the initial 

 incision of the Ohau valley-plain when the cutting of the present trench- 

 like Ohau Valley commenced. This interesting stratigraphic occurrence is 

 shown and explained in the diagrams (fig. 2), and no further comment is 

 necessary here other than to emphasize its bearing on the question raised. 



The Origin and Nature of the Sandstone Formation. 



The evidence outlined above, by proving that the sandstone formation 

 lies upon the river-fans, and not vice versa, places serious difficulties in the 

 way of an acceptance of Cotton's theories of a prograded strand-plain com- 

 posed of gravel fans and peneplaned sand-dunes. The theory is forced to 

 demand a gradual secular subsidence of the area of deposition in order 

 to account for old land-surfaces contained within the gravel fans and now 

 depressed, in some cases hundreds of feet, below the present sea-level ; it 

 relies on the supply of an immense amount of waste with which to main- 

 tain its existence in the face of prolonged subsidence ; and it postulates 

 occasional small movements in a reverse direction to enable retrograda- 

 tions of the coast-line under wave-attack to advance not more than about 

 half its former prograded width. The last precludes all possibility of a 

 movement of uplift on a fairly large scale, certainly not more than 100 ft. 



