Thomson. — Geology of MichUt Clarence and Ure VaJIei/s. 309 



serpentinous character " in the lower slopes of the range, near the mouth 

 of the gorge. Between the Dee and the Mead River McKay notes the 

 presence of numerous dykes of grey porphyritic syenite and dark porphy- 

 ritic hornblende rock intersecting the older rocks of the higher part of the 

 range. From the Mead to Blue Mountain the higher ground is unexplored 

 geologically, but the presence of dykes may be inferred from the boulders 

 present in the gravels of the Swale. The summit of the Blue Mountain 

 and for a considerable distance the spurs descending from it are composed 

 of a dark, coarse-grained dolerite, which weathers to a gritty waste in 

 places covered with a reddish, dry soil. There are lighter-coloured patches 

 with.in the intrusion, the forms of which were not clear. On the spur 

 running from the upper end of the Ure Gorge to the summit the junction 

 with the pre-Notocene rocks was observed. The latter strike north-east at 

 this point, and dip almost vertically, but a little lower down they are 

 sharply contorted. There appeared to be a contact mineral in the argil- 

 lites near the junction, but it was too much weathered for microscopical 

 determination. At the observed junction the intrusive rock was light- 

 coloured and finer-grained than elsewhere, and other fine-grained specimens 

 were observed in the screes higher up. I have noted below the occur- 

 rence, at a lower level in the Blue Mountain Stream, of fine-grained dark 

 dykes invading the Clarentian. Before the formation of the great Clarence 

 fault these rocks presamabiy stood at a high level, and may be apophyses 

 of the Blue Mountain intrusive. 



So little geological exploration of the pre-Notocene rocks of the Looker- 

 on Range has been made that little can be stated as to the abundance of 

 intrusive rocks. I noted the presence of a moderately coarse doleritic dyke 

 a little on the Reserve side of tlie saddle on the pack-track between the 

 Reserve and Quail Flat. McKay records the presence of some dykes of grev 

 intrusive rock, judged to be diorite, on the east side of the range, north- 

 east of the Kahutara gorges, and dykes of a darker colour and basaltic 

 character on the western side of the same part of the range. A fair 

 percentage of coarse- and medium-grained doleritic rocks is present in the 

 gravels of the Hapuku River, proving the presence of intrusives in the 

 north-east part of the Looker-on Range. McKay states that he is informed 

 that in the gravels of the George River, entering the Lower Clarence on 

 the south side, there is so great an abundance of dark-coloured crystalline 

 boulders as to make it comparable in this respect with the Dee or the 

 Branch. I observed a boulder of lustre-mottled hornblendic rock in 

 Heaver's Creek, but as this occurred below the outcrop of the great 

 Marlborough conglomerate it is unsafe to make any deductions from it as 

 to the presence of dykes in the headwaters of that stream. The tributaries 

 of the Wharf, draining the other side of the Sawtooth Range, contain no 

 boulders of igneous rocks above the outcrops of the Clarentian conglomerates . 



McKay has described a great number of intrusive rocks in the country 

 north-west of the Awatere River, and from his descriptions they seem to 

 resemble those of the Kaikoura Range. 



'o^ 



The Notocene Rocks. 

 So far as Notocene geology is concerned, the east coast of the South 

 Island may be divided into two main diastrophic districts, characterized 

 by the age and nature of the middle limestone member, the dividing-line 

 being the Rakaia River. The southern district has as the middle member 

 of its sequence a relatively shallow-water and mainly bryozoan limestone,. 



