STRUCTURAL FEATURES OF N.Z. 215 



■cross set of faults. The conclusions of the author are generally in 

 support of McKay's theory of the presence of a series of great earth 

 movements which are responsible for the landscape features of this 

 part of New Zealand, an opinion which is virtually endorsed by 

 Morgan in his Bulletin on the Mikonui sub-division of Westland. 

 In this publication Morgan reports the occurrence of a great thrust 

 plane at the western edge of the Serpentine belt, with a series of 

 parallel and related minor displacements. He concludes that the 

 thrust which produced the Southern Alps came from the east, and 

 that to the west are sedimentaries which are folded in a direction at 

 right angles to the general trend of the Alps. From this he ap- 

 parently concludes that there was a range to the west of the present 

 coastline in early tertiary times and that the anomalous folding of 

 these beds is the folding of a partly submerged block of country. In 

 connection with this observation of a strike at right angles with the 

 direction prevailing in the Alps, it may be mentioned that directions 

 corresponding to this are to be observed on the Canterbury side of 

 the range (Cox, Geological Report, 1884, page 25) ; another marked 

 variation in strike is also recorded by him on page 28 of the same 

 report. His first observation has been confirmed by Capt. Hutton 

 and the present author. The latter observation serves to show that 

 *beds in undoubted sequence show a marked range of variation in 

 strike over small areas, so that deductions as regards direction made 

 from a variation in strike of the Greenland series, as recorded by 

 Morgan, must be taken with great caution. 



The observations conducted by the present writer in the 

 Arthur's Pass Tunnel show that the beds cut by the tunnel vary 

 from a direction parallel with it — that is, N. 8° W. to N. 23° E. in a 

 distance of about half a mile. The beds are faulted in directions 

 approximately parallel to the latter direction, with very occasional 

 cross faults. The amount of throw in each case it was impossible 

 to determine, as the beds are very monotonous and the tunnel cuts 

 at a small angle the axis of an anticline. It was pointed out by 

 Dobson that the direction of the folds of this part of the Southern 

 Alps is not parallel to the general direction of the range, but about 

 N. 15° E. Although the range has a general north-easterly trend, 

 the folding is in places remarkably discordant with it. 



Papers dealing with the geological structure of the south of New 

 Zealand have been published by Finlayson and the present author. 

 The former describes the different vein systems of Central Otago, 

 and concludes from their distribution and general orientation as 

 follows : — " The fissures are evidently due to compression forces, as 

 they have all the typical features of compression veins, described 

 by Emmons." In his opinion they were caused " by a tectonic 

 force acting from west to east and south-east, with its greatest 

 intensity at the head of Lake Wakatipu, in the near vicinity of the 

 belt of igneous rocks which were intruded during the Jurassic 

 mountain formation. Such a compression movement would con- 

 ceivably extend its area of effect — and would gradually diminish 

 in intensity as it passed towards the coast." 



