[Read before the Philosophical Institute of Canterbury, 7th August, 1890.]
The structure of the Bluff Peninsula has been lately described by Mr. James Park in a report to the Director of the Geological Survey of New Zealand.† It is composed partly of sedimentary sandstones and slates, which are referred by Mr. Park to the Te Anau series, from lithological characters, and partly of eruptive rocks which have usually been called syenites.‡ There are also diabasic-ash breccias, which, as Mr. Park points out, prove that volcanic activity was exhibited during the period of deposition of the sandstones. In fact, Bluff Hill is the stump of an old volcano.
[Footnote] † “Reports of Geological Explorations,” 1887-88, p. 72, with map and sections.
[Footnote] ‡ Dr. C. Forbes, Quar. Jour. Geol. Soc., vol. ii., 1855, p. 522; Hector, in Otago Provincial Gov. Gazette, 5th November, 1863; Hutton, Reports Geol. Expl., 1871-72, p. 102; Geology of Otago, Dunedin, 1875, p. 41; Hamilton, Trans. N.Z. Inst., vol. xix., p. 452.
A few years ago I examined two rocks in my possession, from the Bluff Peninsula, and found one to be an enstatite diorite, the other a hornblende porphyrite.*
Last summer I had an opportunity of visiting the Bluff for a few hours, and I then collected other specimens of rocks, of which I offer short descriptions.
[Footnote] * Jour. of Roy. Soc. of N.S. Wales, vol. xxiii., 1889, pp. 128 and 129.