Adkix. — Fost-tertiary Geological Ififfiory of Oliau River. 501 



gorges, between the Mill and Square Knob Ranges, to the present junction 

 of the Makahika and Wai-iti Rivers, and from thence, in coml)ination with 

 those streams, down the Makahika Valley. Owing to the ruggedness of the 

 locality and to its covering of dense bush, the exact nature and limits of 

 this old suspected course have not been ascertained, but it is probable that 

 it was similar in character to the branch of the " valley plain " which for- 

 merly occupied the Lower Makahika Valley, The position of this suspected 

 course has been shown in the maps of Horowhenua in the early and middle 

 Pleistocene periods, but has not been included in the accompanying geo- 

 logical map. 



After the Ohau River had graded its bed and built up the surface of 

 its fan and " valley plain " until it had attained its maximum altitude 

 it deposited upon the upward extensions and the widest portion of the 

 latter a superficial layer of clay varying from 10 ft. to 30 ft. in thickness. 

 The precipitation of such fine sediment as clay alluvium was an indubitable 

 indication that the cycle of deposition on the part of the Ohau River was 

 coming to a close, and that very soon it would be flowing at grade — pro- 

 bably for the first time in its existence. 



Table sjiowixg the Sui'kkficial Dip of the " Valley Plain " and of the Fan 



OF THE Ohau Rivee. 



From the upper part of the " valley plain " (near the 

 junction of the Makahika and Wai-iti Rivers) 



To the middle part of the " valley plain " (near the 

 junction of the Makahika and Ohau Rivers) 



Ft. 



777 

 582 



From the middle part of the " valley plain " (near the 

 junction of the Makahika and the Ohau River) 



To the lower part of the " valley plain " (near the head 

 of the Levin water-races) 



,^82 



.367 



From the lower part of the " valley plain " (near the head 



of the Levin water-races) 

 To the apex of the Ohau fan 



367 



345 



Ch. 

 164 



105 



43 



95-12 



163-80 



40-93 



