]U 



Transactions. — Geology. 



made iu the liniestoues in the places named above, and the 

 drainage from the west and north-west began to flow as at 

 present, though at a much higher leveh 



But the shingle-conglomerate and other deposits of this 

 old plane of denudation are not merely found flanking the 

 Euahine and Kaiwaka Mountains : similar deposits are very 

 largely developed near Pohui, on the Napier-Taupo Eoad, and 

 are found flanking the Maungaharuru limestones and occupy- 

 ing a large valley in that district as far as the 39th parallel. 

 These conglomerates and allied deposits spread over a great 

 extent of country, aiid they occupy the entire valley from 

 Wairoa, via Pohui, to the Seventy-mile Bush. 



For a long time it had been a great puzzle to me to ac- 

 count for the existence of extensive deposits of a somewhat 

 indurated sandstone, pumice, and conglomerates, especially 

 about Pohui and to the north-east of that place. There are 

 no slates or fine sandstone rocks to the east or north-east of 

 Pohui iu the direction of the Mohaka Eiver. At Tauranga- 

 kuma, fifteen miles or so further to the west, and overlooking 

 Tarawera, the Maitai slates, belonging to the Carboniferous 

 system, are met with for the first time when proceeding from 

 Napier ; but between the two places there intervene the Mau- 

 ngfiharuru limestone range, the Mohaka Eiver valley, certainly 

 900ft. in depth, and the Te Hauroto limestones, clays, and 

 gi'its. That there has been a break in the Maungaharuru 

 Eange the Te Waka scarp is a sufficient proof. There is, how- 

 ever, no trace of shingle, that I am aware of, on the range at 

 a greater height than 350ft. above the present bed of the 

 Mohaka Eiver. 



But the great conglomerate area in the vicinity of Pohui 

 must be accounted for, and that from a source of origin cor- 

 responding to the products. Now, the only possible district 

 from which the deposits could have been derived lies still 

 farther to the westward than the districts named ; and I am of 

 the opinion that the filliug-up of the Polmi valley and surround- 

 ing country was brought about by the same processes that are 

 now at work bringing their loads of debris — shingle, pumice, 

 &c. — from the west to the east. Those who are acquainted 

 with the Euahine and Kaiwaka Mountains are aware there are 

 great breaks in them, through which pass the Mohaka, Nga- 

 rurora, and Tutaekuri Eivers. These breaks correspond to 

 the present system of drainage. 



From the mountains named there formerly extended a vast 

 area of limestone country : in fact, limestone, towards the 

 close of the Tertiary period, seems to have been the only rock 

 exposed in the whole of the district, with the single exception, 

 perhaps, of the chalk-marls in the hills known as the Alps, at 

 Kaikora. At the time to which reference is now being made. 



