134 Transactions. 



taken place about a hinge-line, depression being confined to the western 

 side of this, while to the east there is evidence of uplift only. The tilted 

 block affected by this movement is elongated in a north-north-east and 

 south-south-west direction, and is bounded on the east by a well-marked 

 fault-scarp which forms the eastern front of the Rimutaka Range (Cotton, 

 1916, p. 318) and the fault-coast of Palliser Bay. 



As will be shown below, this movement took place very recently. Such 

 strongly differential movement of a small earth-block in very recent times is 

 unusual even in New Zealand, though it was common enough in somewhat 

 earlier times when the mountain masses were blocked out and the river- 

 courses determined by the movements to which the name " Kaikoura " has 

 been applied (Cotton, 1916). Since the Kaikoura orogenic movements took 

 place throughout New Zealand a very great deal of erosion has occurred, 

 but in the Port Nicholson area, on the other hand, the later stages at least 

 of the tilting, warping, and faulting deformed and dislocated a land-surface 

 the relief of which had already become very nearly that of the present day. 



The features here described may perhaps be correctly ascribed to a 

 modern local recrudescence of the Kaikoura movements. It is interesting 

 to note in this connection that the latest movement which affected this 

 area — that which accompanied the earthquake of 1855 — tilted a block of 

 considerably greater width, though bounded on the eastern side by the same 

 fault, and that the whole district here described was uplifted, including 

 the previously depressed harbour area (Lyell, 1868). It is as though the 

 events which led to the formation of the harbour-depression were a belated 

 reversion to the Kaikoura type of movement, resulting in strong local 

 deformation of the surface, interrupting the more stately movements of 

 larger blocks now in progress throughout the New Zealand region. The 

 fact that the 1855 movement was of the latter type has led the writer to 

 suspect that even in the Port Nicholson district such movements are now 

 normal, and to formulate a working hypothesis that a succession of nearly 

 uniform uplifts preceded the warping and tilting that formed the Port 

 Nicholson depression. The real succession of movements has not yet been 

 worked out with certainty, however, and some puzzling features still 

 remain unexplained. 



It is highly probable that the warping or tilting responsible for the 

 features here described did not go on continuously and rapidly as a single 

 event, but was broken by pauses of considerable length. Little more than 

 the general evidence can be considered at present, however, as it has not 

 yet proved possible to separate satisfactorily the evidence of successive 

 movements. 



The Evidence. 



Summary. 



The evidence of tilting and warping on the eastern side of the Port 

 Nicholson depression is of three kinds : (1) Tilted uplifted coastal platforms, 



(2) progressively more extensive drowning of valleys from the hinge-line 

 of tilting to the axis of maximum depression (which is accompanied 

 by rejuvenation of the valleys on the other side of the hinge-line), and 



(3) evidence of regrading in warped valleys, particularly aggradation in 

 such as are tilted backward. 



The evidence under the first two heads is found in one line of section 

 only, that formed by the sea-coast, while that under the third head can be 

 seen at a number of places along the eastern boundary of the depressed area. 



