Speight. — Structural and Glacial Features of Kurunui Valley. 105 



The dismemberment of the ridges would no doubt be promoted bv the 

 sapping-back of the valley-walls and their complete reduction in places 

 where the ice-stream impinged more powerfully. If we compare the results 

 of the glaciation in other valleys we see that in their cases the dismember- 

 ment has been more complete, the dissection of the dividing ridges carried 

 to a further stage, and the straightening of their sides more thoroughly 

 carried out. because they experienced more complete glaciation. If we were 

 furnished in these cases with more clear indication of the intermediate 

 condition of the direction of drainage it would be possible to reconstruct 

 the original stream-system. 



There is one point, however, which has not been considered fully — 

 viz., the agreement in the direction of the tributary valleys with those of 

 the Waimakariri and Rakaia. Is this agreement in orientation the result 

 of accident, or is it based on some structural condition which has influenced 

 the country in the basin of the Hurunui as well as the country farther south '. 



I have shown (1916, pp. 142-43) that there exists in the mountain region 

 of Canterbury a well-marked series of fractures or lines of folding which 

 lie in a north-west and south-east direction. Cotton (1917, p. 273) draws 

 special attention to the importance of the north-west system of earth- 

 fractures in Otago as compared with the other parts of this Island, but 

 they certainly occur in Canterbury in conjunction with the Kaikoura 

 system, and it is possible that in the upper Hurunui, as in the Waimakariri, 

 they are co-existent. Since writing the article referred to above I have 

 noted additional lines with the north-west orientation, especially in the 

 upper valley of the Waipara and in South Canterbury in the country between 

 Fairlie and Cave. In both these cases there are undoubted, well-marked 

 lines of fault. It is possible, therefore, that the general direction of the 

 valleys at the head of the Hurunui were determined initially by lines of 

 structural weakness. It is remarkable also that some of the valleys on the 

 northern side of the river have a characteristic east-north-east orientation, 

 and these are parallel to other valleys farther north, such as the Hope, in 

 the basin of the Waiau. On the line of one of these upper valleys is the 

 hot spring which forms a notewerthy physical feature of the Upper Hurunui, 

 and I am informed that other springs occur in the valley which stretches 

 north-east from this locality. This certainly points to the presence of an 

 earth -fracture with east-north-east orientation. 



Another feature of this district should be noted — viz., the north-and- 

 south trend of the upper valleys of the Waiau and Clarence, a direction 

 which is parallel to the twin valleys of the Mandamus, and to that of the 

 Glenrae, lying to the west of these. The arrangement may be only a 

 coincidence, but it is certainly a striking one. 



Bibliography. 



Cotton, C. A., 1914. The Physiography of the Middle Clarence Valley, New Zealand.. 



Geo;/. Journ., vol. 42, pp. 225-46. 



1917. Block Mountains in New Zealand, Am. Journ. Sci., vol. 44, pp. 249-93. 



Haast, J. vox, 1871. Rep. Geol. Explor. dur. 1870-71, pp. 30, 48, sections. 



■ 1879. Geology of Canterbury and Westland, pp. 69-78, 216-17. 



Hutton, F. W. ; 1877. Rep. Geol. Explor. dur. 1873-74, pp. 34-35, 55-56. 



— 1889. The Eruptive Rocks of New Zealand, Trans. Urn/. Soc. N.S.W., vol. 23, 



pp. 125. 15li. 

 Speight, R., 1915. The Intermontane Basins of Canterbury, Trans. N.Z. Inst., 



vol. 47. pp. 347-48. 

 101 (i. The Orientation of the River-valleys of Canterbury, Trans. N.Z. Inst., 



vol. 48, pp. 137-44. 



