308 Transactions. 



Rivers, he describes as crowded with dark basic dykes, which can be traced 

 into the pre-Notocene of the Kaikoura Range. The evidence of the Claren- 

 tian basal conglomerates is to this extent favourable to McKay's division 

 of the rocks : that the only igneous rocks included in them in either the 

 Clarence or the Awatere Valleys are granites, microgranites, and cjuartz 

 porphyries. Typical granites or quartz porphyries, however, have not yet 

 been found in the Kaikoura or Looker-on Ranges, and I incline to the 

 opinion that the syenites belong to the same period of vulcanicity as the 

 more basic intru^sions, and that this period is coincident with the outpour- 

 ings of Clarentian lavas in the upper parts of the Middle Clarence and 

 Awatere Valleys. There are four reasons for this belief. In the first place, 

 such a differentiation series is common in intrusive rocks, as witness the 

 association of granophyres and quartz dolerites with the Tertiary volcanic 

 rocks of the British Isles. In the second place, intrusions in the greywacke- 

 argillite series of both Islands of New Zealand are rare, whereas in the 

 Kaikoura Range they are abundant, and lie between two prominent 

 developments of Clarentian lavas. In the third place, boulders of the 

 svenites appear to be totally absent from the great Marlborough conglome- 

 rate, suggesting that they had not been uncovered by erosion at the time 

 of its formation. Finally, and most conclusively, I observed that the 

 syenites on the spurs leading to Mount Tapuaenuku contained frequent 

 inclusions and schliere of camptonitic facies. 



In the ascent of Mount Tapuaenuku I observed occasional dense 

 amvgdaloidal dykes in the pre-Notocene rocks of the upper Dee. At 

 about 6,000 ft., "on the spur between the Dee and the Branch, the pre- 

 Notocene rocks have a strike a few degrees west of north. The upper 

 part of this spur, right to the summit, is composed of a reddish syenite, 

 intersected by innumerable dark dykes 1 ft. to 2 ft. thick, which have 

 mostly an east- west trend (Plate XXIV, fig. 2). The neighbouring spurs on 

 each side appear to have the same character. On the exterior these dykes 

 are often dense, but in the centre coarsely crystalline. This proves that 

 the syenite had cooled sufficiently to be fissured before the intrusion of the 

 dark dykes, and perhaps even sufficiently to chill the margins of the dykes, 

 although tachylitic selvages were not observed. The dark dykes, however, 

 are intersected and faulted by one another, proving that they were injected 

 at sufficiently distant intervals to permit of consolidation before the next 

 intrusion. 



The greatest development of the intrusives is undoubtedly in the Tapuae- 

 nuku massif, but they are probably present in smaller number throughout 

 the range. In the upper Muzzle,' McKay states that " the sedimentary 

 rocks are more rapidly degraded than the trap-dykes intersecting them, 

 so that the latter, traceable for long distances, form a remarkable feature 



in a wild and rugged landscape The brecciated slaty beds 



and mudstones are broken up and so rapidly removed from the slopes 

 of the range on the east side of the creek that the dykes project various 

 heights above the general surface. They trend for the most part north, 

 between barren slopes of black shingle, while a lesser number of dykes 

 running south-east, and some of them east, enclose areas which, while the 

 barriers stand, are completely walled around. The greater number of the 

 dykes trend north, and pass into or under the cluster of peaks south of 

 Tapuaenuku." (McKay, 1886, pp. 50, 51.) 



Judging from the small number of igneous boulders in the Bluft" River, 

 McKay considers it clear that comparatively few dykes are present in the 

 mountains drained by it, but he observed " several massive dykes of a 



