[1] Mr. J. Starkie Gardner, from a recent comparison of the plant-remains of Antrim and Mull, concludes that "that they might belong to any age between the beginning and the end of the warmer Eocene period; and that they cannot be of earlier, and are unlikely to be of later, date."—Trans. Palæont. Soc., vol. xxxvii. (1883).
[2] Having dealt with this district rather fully in The Physical Geology and Geography of Ireland (Edit. 1891, p. 81), and also in my Presidential Address (Section C.) at the meeting of the British Association, 1874, a brief review of the subject will be sufficient here, the reader being referred to the former treatises for fuller details. The following should also be consulted: Gen. Portlock, Geology of Londonderry and Tyrone (1843); Sir A. Geikie, "History of Volcanic Action during the Tertiary Period in the British Isles," Trans. Roy. Soc. Edinburgh, 1888; and the Descriptive Memoirs of the Geological Survey relating to this tract of country.
[3] Owing to the superposition of the basaltic masses on beds of chalk throughout a long line of coast, we are presented with the curious spectacle of the whitest rocks in nature overlain by the blackest, as may be seen in the cliffs at Larne, Glenarm, Kinbane and Portrush. (See [Fig. 27].)
CHAPTER II.
SUCCESSION OF VOLCANIC ERUPTIONS.
(c.) First Stage.—The earliest eruptions of lava in the North-east of Ireland belonged to the highly acid varieties, consisting of quartz-trachyte with tridymite.[1] This rock rises to the surface at Tardree and Brown Dod hills and Templepatrick. It consists of a light-greyish felsitic paste enclosing grains of smoke-quartz, crystals of sanidine, plagioclase and biotite, with a little magnetite and apatite. It is a rock of peculiar interest from the fact that it is almost unique in the British Islands, and has its petrological counterpart rather amongst the volcanic hills of the Siebengebirge than elsewhere. It is generally consolidated with the columnar structure.
| Fig. 29.—Part of the section shown in the quarry at Templepatrick, showing the superposition of the basalt (d) to the trachyte (b), with the intervening bed of flint gravel (c). All these rocks are seen to rest upon an eroded surface of the Chalk formation (a). |