PAPEKS. 



ON THE GEOLOGY OF THE NEW ZEALAND ALPS. 

 By Captain F. W. Hutton, Cobb. M.R.S., op Tasmania. 



[Bead April 13th, 1886.] 



The New Zealand Alps form a narrow range of 

 mountains dividing the plains of Canterbury from those of 

 Westland, and attain in Mount Cook an elevation of 12,349 

 feet. Both to the north and to the south they widen 

 out into several subordinate ranges with peaks from 6,000 to 

 nearly 10,000 feet in height. The principal snowfields and 

 glaciers occur in the central portion between the sources 

 of the River Rakaia and those of the Waitaki; but small 

 glaciers are found as far north as the head of the Waimakariri, 

 near the West Coast Road, and as far south as Lake 

 Wakatipu and Milford Sound. The largest glacier is the 

 Tasman, which lies on the eastern side of the range just north 

 of Mount Cook and which, according to the survey of Dr. 

 von Londenfeld, is rather more than twenty miles in length 

 by nearly two in breadth ; its terminal face being 2,450 feet 

 above the sea. On the western side of the range the glaciers 

 are smaller, but descend much lower ; the Francis Joseph 

 glacier reaching to 705 feet above the sea. This is owing 

 partly to the greater snowfall, and partly to the steeper 

 slope on that side of the mountains. 



Nearly the whole of the Alps are composed of much 

 disturbed sedimentary rocks, principally sandstones, mud- 

 stones, and greywackes. The main anticlinal, or true tectonic 

 axis, runs in a south-westerly direction from Tasman's Bay 

 to Otago, where it curves round to the south-east, and 

 reaches the sea near Dunedin. The central parts of this 

 anticlinal aro composed of Schists of different kinds. The 

 tectonic axis, however, nowhere coincides with the 

 orographic axis of the range, but lies along its western 

 base in Westland, where the whole of the western portion 

 of the elevated massif has been removed by denudation, 

 so that the main ridge of the Alps is carved out of the south- 

 easterly face of the anticlinal curve. To the north and to 

 south of the Alps proper, both wings of the anticlinal remain. 

 West of this main anticlinal a synclinal runs through the 

 provinces of Nelson and through Southland, lying parallel 

 'with the anticlinal; but on the eastern side the rocks are 

 more irregular, there being several synclinals and anticlinals 



