318 Dr. C. A. Cotton—Later Geological 
The district around Wellington and that characterized by a con- 
tinuation of the outcrop of ‘oldermass’ rocks to the north-eastward 
—the axis of the island—has not, however, escaped uplift; and 
a very general sudden steepening of the dip of the younger strata as 
the oldermass is approached shows that this uplifted block or series 
of blocks is bounded by monoclinal flexures or faults.’ 
Along the eastern base of the Rimutaka Range there is a well- 
preserved fault-scarp. Here the structure closely resembles that 
produced by the Kaikoura movements in the South Island. To the 
east lies a gently tilted block with its cover much folded; and a broad 
fault-angle depression—the Wairarapa Valley—exists between the 
black slope of this block and the steep eastern fault-scarp slope of 
the Rimutaka Range. The broad tectonic depression extends far to 
the north-east.” 
East of the mountain axis the effects of compression are strongly 
marked, the covering strata being much folded, while westward 
from the axis they are only very gently tilted. The trend of the 
features produced by these movements is about north-east, as it is in 
the neighbouring part of the South Island. 
In the northern part of the North Island isolated areas of the 
oldermass project through the Tertiary formations. To these Suess * 
refers as ‘isolated fragments of the sunken range”’, and Marshall * 
expresses agreement with Suess’s statement that the ‘‘ north-west 
coast in no way represents the actual trend of the mountains ”’. 
To the writer the presence of these horst-like masses appears to 
indicate that the northern portion, in common with the rest of New 
Zealand, was affected by the Kaikoura movements. From these 
uplifted areas the covering strata have been removed, and the 
oldermass has been maturely dissected. In the neighbourhood of 
the horsts and generally throughout Northern Auckland the Tertiary 
strata are considerably folded. 
Post-Karxkoura MovEmMeENTs. 
It is well known that in comparatively recent times some parts 
of the New Zealand region have been affected by uplift and others 
by subsidence, while in some parts there is evidence of oscillation. 
Very brief reference to these movements is all that is possible here. 
It is important to note, however, that these latest movements 
generally have the effect, as far as any particular district is concerned, 
of ‘regional’ as distinguished from differential movements—of 
epeirogenic as distinguished from orogenic. In a broad sense, 
however, these movements really are differential, for the New Zealand 
region has not moved as a whole. Units of much larger size than 
the blocks associated with the Kaikoura movements have moved 
independently. 
1 J. A. Thomson, ‘‘ Mineral Prospects of the Maharahara District, Hawk’s 
Bay’’: 8th Ann. Rep. Geol. Sury., Mines Statement, 1915, p. 164. 
* Thomson, loc. cit., p. 165. 
3 The Face of the Earth (Eng. trans.), vol. ii, p. 44, Oxford, 1906. 
4 New Zealand and Adjacent Islands, 1911, p. 25. 
