Speight. — Geological Excursion to Lake Tekapo. 45 



Again, the height at which these sediments occur in the Tekapo region 

 is most striking. In Coal River thev are 3,500 ft. above sea-level, and in 

 Stony Creek 4,200 ft.- that is, 2,700'ft. above the floor of the lake. These 

 deposits, especially the latter, could not have been deposited were the 

 form of the Mackenzie basin at all like that at present existing. If the basin 

 had been filled up to this level it would imply the removal of an enormous 

 amount of material by glacier erosion subsequent to deposition, and this 

 amount is too great to have been removed without leaving morp than two 

 slight traces of its former presence in the Tekapo area, even if we grant 

 that glaciers have great powers of erosion. Some remnants other than 

 those would be present, tacked away in some sheltered corner of the 

 mountains out of the line of action of the ice-flood. If warping be called 

 in to modify the form of the basin this argument falls to the ground. 

 It is remarkable, however, that the remnants occur in a region where the 

 mountains are highest. 



If due regard be paid to the character of the deposits it will be evident 

 that the Mackenzie country looks rather to Otago for its nearest relatives, 

 though similar areas occur farther north in Canterbury. In these, lime- 

 stones are a dominant geological feature ; whereas in Otago they are almost 

 absent, the occurrence of patches like that at Bob's Cove, on Lake Waka- 

 tipu, being quite exceptional. The occasional occurrence of marine shells, 

 however, shows that the sea extended over the area. The presence of 

 conglomerates at the close of the cycle of deposition indicates that fairly 

 high land was in existence at that time; and, as similar gravels are found 

 closing the Tertiary sequence over a great extent of country to the east 

 {e.g., the Kowai* series of North Canterbury) and to the west of the Alps, 

 as described in various bulletins of the Geological Survey, it is reasonable 

 to think that the movements which resulted in the final formation of the 

 Alps commenced towards the close of the Pliocene period and continued 

 into the Pleistocene, and therefore that the intermounts date from that 

 time. The final form of the landscape resulted largely from the influence 

 of glaciation on the structural features then formed. 



Little evidence of the direction of the axes of deformation is afforded 

 by the Tekapo district. There is nothing to support the contention of 

 Edward Dobson that the orientation of the valley of the Godley was 

 initially determined by tectonic movements, although I came across nothing 

 against it. The axis of the valley, however, seems to correspond with the 

 general strike of the greywackes and associated rocks. 



The latest observed deformational movements that the district ex- 

 perienced are on north-east and south-west lines. The strike of the coal- 

 beds in Stony Creek, and also the fault-line which bounds the occurrence in 

 Coal River, have this direction. From the limited and unsatisfactory nature 

 of the exposures in the latter locality the general strike of the beds cannot 

 be accurately determined, but the even and regular slope of the north- 

 west side of the Richmond Range suggests that it corresponds with some 

 fault-line ; and, further, if such a line be granted to exist, and its direction 



* Note. — I have retained the spelling for this term in the form as applied 

 originally by myself to the series developed in North Canterbury, although Dr. J. A. 

 Thomson has criticized it and replaced it by another speUing in his paper on the 

 " Geology of the Middle Waipara and Weka Pass District " (Trans. N.Z. Inst., vol. 52, 

 p. 334, 1920). The spelling used by me is that originally used by Haast, and is also 

 that in official use for the past thirty years not only for the river, but for the district, 

 now merged into a county. It is that which appears on all recent maps issued by the 

 Survey Department. Further justification is, I think, unnecessary. 



