Park. — Glaciation of the North Island. 



581 



deposit becomes so well developed as to attract attention. From Turanga- 

 a-rere southward to a point half a mile or so past Taihape the andesitic 

 material is almost continuous, being particularly conspicuous in many of 

 the deep railway-cuttings, and along the coach-road that follows the Hau- 

 tapu Valley. 



A very fine section of the andesitic till is exposed near the 250-mile post, 

 about a mile south of Turanga-a-rere Railway-station. At this place the 

 railway-cutting passes through the glacial drift for a distance of 15 chains, 

 exposing at one place a face 40 ft. high. 



The andesite boulders are mainly angular, semiangular, or partially 

 rounded. They range from a few inches up to over 10 ft. in diameter. 

 And in this cutting there are also seen large angular masses of soft 

 Tertiary sandstone mixed with the andesite blocks. The spaces between 

 the andesite rubble are filled mostly with gritty clays, sandy material, and 

 small pieces of andesite, mixed with a small amount of water-worn pebbles 

 and small boulders. The general appearance of the deposit is well shown 

 in Plates XLV, XLVI, and XLVII. 



Many of the harder andesite blocks present smooth polished surfaces 

 on one side. These surfaces are sometimes undulating or rounded, and 



^ 

 ^ 





-CI- 





A^/V£ 



2S' 





Fig. 1. — Section of Railway-cutting at One-quaetee Mile past Hautapu Falls. 

 a. Pliocene sandy clays. h. Glacial drift. 



sometimes perfectly flat. The polished surface of one boulder presented 

 very distinct striae. 



At the south end of the big bend, about three miles south of Turanga-a- 

 rere, at a point immediately opposite the Hautapu Falls, the andesite till 

 crowns the hills to a height of 300 ft. above the floor of the valley. Over- 

 looking the falls there is a nest of large andesite blocks, one of which 

 measures 8 ft. by 6 ft. by 6 ft., and another 9 ft. by 7 ft. by 6 ft., the weight 

 of the last being about 27 tons. These blocks are large irregular-shaped 

 masses, with one side well polished. A group of these blocks is shown in 

 Plate XLV III. 



It should be noted that the masses of andesite that lie on or project 

 above the surface often show a tendency to assume a more or less rounded 

 shape, through the process of spheroidal weathering which so commonly 

 affects rocks of a basic or semibasic type. 



The surface of the Pliocene clays on which the till rests is generally 

 deeply eroded ; and in many places it has been excavated into grotesque 



