308 Transactions 



Akt. XXXIV. — The Discovery and Extent of Former Glaciation in the 

 Tararna Ranges, North Island, New Zealand. 



By G. L. Adkin. 



[Read before the Wellington Philosophical Society, 6th September, 1911.] 



Plates XXII-XXIV. 



The discovery of evidence of former glaciation in the Tararua Ranges 

 was made by the writer in February,. 1909, and two years later (March, 

 1911) further discoveries were made and the previous ones confirmed. 

 The glaciated areas and the memorials < f former frost-action so far dis- 

 covered are situated on the highest ranges of the Tararuas — viz.. on that 

 part of the Dundas Range lying nearest the geographical centre of the 

 mountain - system, and on the Mitre-Holdsworth Range. During the 

 maximum phase of glaciation the heads of five river-valleys were filled 

 with glacier-ice : (1) Park River,* the main tributary of the Waiohine-iti 

 River, named after the well-known New Zealand glacialist ; (2) the main 

 source of the Waiohine-iti River ; (3) Dorset Creek, a left-bank tributary of 

 the Waiohine-iti River, named after a pioneer explorer of the Tararuas ; 

 (4) Bennington Creek, a tributary of the Waingawa River, rising in the 

 south-west foot of the Mitre Peak, named after a companion of Edward 

 Dorset ; and (5) the Mangaterera River, another tributary of the 

 Waingawa. 



The phenomena resulting from the presence of glaciers now non-existent 

 consist of — (1) U-shaped valleys ; (2) glacial cirques ; (3) rock basins ; 

 (4) glacial hanging valleys ; (5) fluviatile hanging valleys. 



In order to give a clear and correct impression of the extent and cha- 

 racter of former glaciation in the Tararuas, the phenomena tabulated will 

 first be dealt with seriatim, and then the topography of the Park Valley 

 ■ — the locality where these phenomena attained their maximum develop- 

 ment — will be fully described. 



(1.) U-shaped Valleys. 



U-shaped valleys furnish the principal evidence of the former presence 

 of ulacier-ice. So far as is at present known, they occur in five situations. 

 The head of Park Valley is U-shaped for a distance of two miles ; in the 

 Waiohine-iti Valley the same feature extends for about one mile ; in the 

 valleys of Dorset and Bennington Creeks, for about half a mile each ; and 

 at the head of the Mangaterera Valley, about a quarter of a mile. The 

 accumulation of scree-material, talus, and alluvium has to a certain extent 

 obscured the U-shaped form and reduced the original steepness of the 

 walls of these valleys, but even now their special character is unmistakable. 

 Below their U-shaped heads the valleys contract to narrow gorges typical 

 of fluviatile erosion. 



* The river draining this valley has hitherto neither been named nor shown on 

 any available map. On every available map the main source of the Otaki River is 

 represented as draining the site of the upper portion of Park Valley. 



