314 Transactions. 



The most striking feature of the main U-shaped valley is the high 

 development of screes. These bury the precipitous walls to a height of 

 from 250 ft. to 320 ft. above the valley-floor. Above the screes the lateral 

 walls rise to a height of from 50 ft. to 100 ft. In the main cirque the pre- 

 cipices rise 290 ft. above the apexes of the screes. Throughout the greater 

 pajt of its length the floor of the main valley is loaded with scree-material ; 

 the bases of the screes on the one wall meet the bases of those on the other, 

 and the modern drainage- channel of the valley follows the line of contact. 

 The screes are now not in the course of formation, being clothed with 

 tussock-grass and subalpine scrub. 



In the U-shaped section of its valley the Park River is actively engaged 

 in altering the gradient of the valley-floor. In the main cirque it is an 

 aggrading stream, and has there formed an alluvial flat several acres in 

 extent. Below this flat the river flows in a narrow channel of gradually 

 increasing depth. Near the lower limit of glaciation this channel is about 

 20 ft. deep, and the rock floor of the valley, upon which the screes rest, has 

 been incised by the river to a depth varying from 10 ft. to 15 ft. 



The infilling at the head of the valley, and the excavation below, clearly 

 demonstrate that the valley was overdeepened* by the old glacier. After 

 the disappearance of the ice the rock basin was probably the site of a small 

 lake until it was filled in by the accumulation of alluvium. 



Such criteria of former glaciation as moraines, roche moutonnees, and 

 striated surfaces have not been found in Park Valley or in any of the other 

 glaciated areas of the Tararuas. It is highly probable that some of the 

 phenomena enumerated do exist, but in Park Valley, and in the other 

 glaciated localities also, the present excessive accumulation of scree-material 

 and alluvium precludes all possibility of their detection. The apparent 

 absence of a terminal moraine may be accounted for by the small size of 

 the glacier. It may be, however, that some of the angular debris resting 

 on the valley-floor near the lower limit of glaciation is morainic material 

 laid down during the slow but regular shrinking of the glacier during its 

 final retreat. Another suggestion is that the great piles of boulders that 

 encumber the narrow gorges situated immediately below the lower limits 

 of glaciation in Park Valley are the re-sorted relics of a terminal moraine. 

 According to this supposition, the terminal moraine of the old glacier was 

 demolished and carried to lower levels since the disappearance of the ice 

 by the periodic floods of the modern river. In this way the angular blocks 

 forming part of the moraine were rounded and transformed into the 

 boulders as they now exist. The boulders in the gorges referred to are 

 very much larger and more numerous than any that lie within the 

 glaciated upper portion of the valley. 



The following altitudes in Park Valley were determined by the use of 

 an aneroid set by the trig, on Mount Dundas : The saddle in the watershed 

 of the Dundas Range at the head of the largest glacial hanging valley, 

 4,440 ft. above sea-level ; the lip of the largest glacial hanging valley, 

 3,900 ft. ; the lips of the twin glacial hanging valleys, 3,750 ft. ; the centre 

 of the alluvial flat in the floor of the main cirque, 3,380 ft. ; the summits 

 of the precipitous rock walls of the main U-shaped valley — left wall 

 3.800 ft., right wall 3,670 ft.; the lower limit of glaciation (i.e., of the 

 U-shaped part of the valley), 3,000 ft. above sea-level. 



* The glacial hanging valleys furnish additional evidence in favour of this con- 

 clusion. 



