TRANSACTIONS OF SECTION C. 597 



Carboniferous strata of Ballycastle, west of Fair Head, are mainly sandstones with 

 intercalated coal-seams, on the same horizon as the Calciferou.s Sandstone of the 

 South of Scotland. 



A patch of marine Permian strata occurs east of Belfast, at Ilolywood ; and 

 the British type of Trias, red rocks with salt and gypsum, is well represented 

 under the basalt capping that has preserved it. The Rhretic sea spread into this 

 area, and terminated far west against the Londonderry highlands ; the Lias also 

 began to form, and is now finely exposed at Waterloo, close to Larne. It is 

 questionable if higher Jurassic beds than those now left to us were ever laid down 

 in this region ; elevation and denudation certainly set in early, and the country 

 remained dry land until the middle of Cretaceous times. Then, in the western- 

 most extension of the great Chalk sea, the sands, conglomerates, and white lime- 

 stone of Antrim were deposited, representing the Upper Cretaceous of England in a 

 thickness of about 100 feet. The cliffs of hardened chalk, between red basement- 

 beds of Trias and the black basalt scjirp above, form, in Glenarift' and Murlough 

 Bay, one of the most beautiful contrasts in our islands. It is clear that in early 

 Eocene times both the counties of Antrim and Down were covered with a rolling 

 series of chalk uplands, resembling on a less massive scale our present Salisbury 

 Plain. This quiet and newly upheaved country was destined to be devastated by 

 Tolcanic action, more continuous and extensive than had been seen in the British 

 Isles since Old Red Sandstone times. 



The ground v/as first broken by rifts running from south-east to north-west, 

 and these were quickly filled by basic lavas. Flow after flow emerged across the 

 country, filling up the hollows carved by denudation, and forming in time con- 

 tinuous plateaux. Although a few explosive vents were established here and 

 there, fluid basalt was the great feature of these eruptions. A time of quiet 

 followed, when the lake-deposits and iron ores of Glenarm, Ballypalady, &c., were 

 accumulated ; and sporadic outbreaks of rhyolite appeared, the most prominent 

 being that of Tardree Mountain. Then the basic eruptions were renewed, and 

 the columnar basalts of the Causeway coast belong to this second epoch of 

 activity. 



Mr. Starkie Gardner has referred these volcanic masses of Northern Ireland to 

 early Eocene times, from a study of the plant-remains in the associated lake- 

 deposits. Plence we find the marine Cretaceous beds followed by a terrestrial and 

 igneous Eocene ; and possibly some of the latest vents were active in Oligocene 

 times. Thenceforward we know nothing of Irish geological history until the 

 glacial epoch, which has left such piles of boulder-clay and gravel across the 

 countrj'. The latest feature of interest is the blue marine clay of Belfast and 

 Magheramorne, full of exquisitely preserved post-Pliocene fossils. This lies 

 unconformably on the glacial drift, and represents a comparatively recent sub- 

 mergence and re-elevation. The raised beach of Larne, with flint-chips in it 

 prepared by man, indicates the modern date of the movements of elevation. 



When we go south from the immediate neighbourhood of Belfast, the Mourns 

 Mountains rise conspicuously, their summits being far more bold than those of 

 the adjacent Caledonian granite ridge. They are also formed of granite, which 

 cuts across basic masses ; the latter are seen at Carlingford to be at any rate post- 

 Carboniferous. In turn, a few basic dykes of still later date traverse the granite. 

 By its relation to these two basaltic series, and its petrographic identity with the 

 Cainozoic granites of Mull and Skye, we need not hesitate to regard the Mourne 

 granite as of Eocene age. It forms, then, as Mr. McHenry has pointed out, an 

 interesting deep-seated mass for comparison with the rhyolitic lavas of the inter- 

 basaltic epoch in Co. Antrim. 



From the above notes, which have no claim to originality, it will perhaps be 

 seen how attractive the Belfast area is to geologists, by reason of its very contrast 

 with the accepted types of Jurassic, Cretaceous, and Cainozoic deposits, as known 

 to us in the London Basin. Those familiar, on the other hand, with the geology 

 of the Scottish Isles, will find many interesting points of similarity. 



