578 Transactions. 



glacier westward towards the Turakina. The Kaimanawas and Ruahine 

 Ranges are composed of argiUite and greywacke ; hence the Rangitikei 

 :'glacier, until it met the Hautapu glacier near Utiku, carried only argillite 

 and greywacke boulders. 



In the Manawatu district, the fluvio-glacial coastal drift is composed 



mainly of greywacke ; and in the Rangitikei area, of greywacke with a 



I sprinkling of andesitic material. Going westward, the andesitic material 



^becomes more and more abundant, until at Wanganui it forms the bulk 



of the drift. 



The andesitic glacial drift in the Hautapu Valley was first discovered 

 by me during the progress of my geological reconnaissance* of the Main 

 Trunk Railway route in 1886-87 ; but on account of the dense forest I was 

 unable at that time to determine whether the boulders were connected 

 with some local volcanic centre or derived from Ruapehu. 



The construction of roads and railways has now enabled me to deter- 

 mine the true character of the deposit ; while the clearing of the forest 

 has revealed the glaciated outlines that were then hidden ii'om view under 

 a mantle of almost impenetrable vegetation. 



Ruapehu lies in latitude 39° 15' S.— that is, 1° 30', or 100 miles, further 

 north than Boulder Lake, in Collingwood, the most northerly point at which 

 evidence of ancient glaciation is known in the South Island. The latitude 

 of Boulder Lake is about 40° 45' S., and of Wellington Harbour 41° 7' S. 



The manner in Avhich glacial drifts were deposited or formed by glaciers 

 is always difficult to explain, on accoimt of the extremely variable character 

 of the deposits. The most satisfactory explanations are always open to 

 doubt. The Hautapu drift is too widespread and variable to be described 

 as a terminal or lateral moraine, and I am inclined to think that it must 

 be regarded as a boulder-clay or till formed mainly of intergiacial debris 

 deposited by the Hautapu glacier as it retreated to its centre of movement 

 at Ruapehu. Such material would become in a measure infraglacial when 

 the upper stream in which it was imbedded flowed over the divide into the 

 Hautapu Valley. Besides andesite blocks, the drift in places contains 

 angular masses of shelly limestone, sandstone, and calcareous nodules 

 derived from the Pliocene series over which the ice crept. 



The marine-clay series on the denuded surface of which the till rests has 

 always been grouped in the Wanganui system of Pliocene age, which there- 

 fore limits the New Zealand glacial period to the Pleistocene — that is, the New 

 Zealand ice age was synchronous with that of the Northern Hemisphere. 



Ruapehu attains a height of nearly 9,200 ft. It carries permanent 

 snowfields, and its great crater-basin is filled with what may be termed 

 a smnmit glacier, or icefield. In the Pleistocene this mountain was a 

 centre of dispersion from which glaciers radiated into the Rangitikei, 

 Wangaehu, Upper Wanganui, and Upper Waikato, the glacier in the last 

 flowing into the Taupo Basin, through the Rangipo Desert. 



With respect to the glaciation of the North Island generally, I think 

 it probable that further research will lead to the discovery of evidence in 

 many other places — notably at Newtown, Karori, and Johnsonville, in the 

 vicinity of Wellington ; in the Wairarapa, near the Tararuas ; and on the 

 east side of the Ruahine Range — -notably in the neighbourhood of Woodville, 

 and east of that towards the sea. 



* J. Park : Reports of Geol. Expl., 1886-87, p. 69. 



