600 Transactions. 



conspicuous that it seems hardly possible for the one to be mistaken for 

 the other. 



The area at present known to be covered with this glacial till is some 

 two or three hundred square miles, but it is not improbable that the 

 clearing of the forest will show that it stretches far to the westward of 

 the Hautapu. 



The Rangitikei glacier descending from the Kaimanawa Range carried 

 only greywacke blocks, and on account of its greater mass it forced the 

 Hautapu glacier to the westward. The effect of this deflection is well seen 

 in the fluvio-glacial drift that forms the great coastal plain extending from 

 the Manawatu to the Wanganui Valley. In the Manawatu area the drift 

 is entirely composed of greywacke material ; in the Rangitikei area, of 

 greywacke and andesite, the former predominating ; while in the Wanga- 

 nui area the boulders are mainly andesitic. 



In the North Island the evidence of ancient glaciation has been de- 

 scribed by me as far north as 39° 15' S. latitude, and I am strongly of 

 the belief that further investigation will extend the northerly limit con- 

 siderably beyond this. 



When discussing my paper on the glaciation of Ruapehu region and 

 Rangitikei Valley,* Dr. Marshall dissented from my views both as to 

 the evidence of glacial erosion and the glacial origin of the sheet of ande- 

 sitic detrital material covering the Hautapu Valley. It is, of course, open 

 for any one to dissent from my interpretation of the genesis of the surface 

 forms — the acceptance of evidence as to glacial erosion is proportional to 

 the observer's ability to interpret aright the signs of extinct glaciers ; but 

 in respect to the sheet of andesitic material the case is altogether different. 

 When I discovered this deposit in 1886, so numerous, large, and angular 

 were the piles of andesitic blocks of which it was composed, as then exposed 

 in slips and where cut through by streams, in the dense forest then covering 

 the Hautapu Valley, that I describedf and mapped it as " volcanic 

 agglomerate and tuff," derived either from some local volcanic centre or 

 from Ruapehu. I am confident that any one who now views the piles 

 of angular volcanic material exposed in the railway cuttings along the Main 

 Trunk line between Mataroa and Taihape will pardon the error I un- 

 wittingly fell into in the year 1886. 



Dr. Marshall also objected to the glacial origin of the till because I had 

 made no mention of the occurrence in it of perched blocks. This was 

 merely an omission on my part. As a matter of fact, many large erratic 

 blocks of andesite occur perched on the slopes and summit of the papa 

 hills near Kaikoura Stream, a short distance south-west of Utiku— that is, 

 at the extreme south limit of the deposit, over forty miles from Ruapehu, 



He further objected that no striated boulders had been found in the 

 drift. So far no striated stones have been seen, and I think it is 

 improbable that such will ever be found, as the underlying papa or blue 

 clay is so soft that it could not, in my opinion, offer sufficient resistance 

 to cause the striation of the harder andesite blocks dragged along by the ice. 



But striated blocks are not always present in glacial deposits, their 

 occurrence depending on the character of the bed-rock and the resistant 



* J. Park, " On the Glaciation of Ruapehu and Rangitikei Valley, Wellington," 

 read before Otago Institute, 10th August, 1909. 



t J. Park, " On the Geology of the Western Portion of Wellington Province and 

 Part of Taranaki," Rep. Geol. Exp., 1886-87, p. 69. j 



