THE EOCENE SERIES 547 



lower lavas rest on an irregular floor of older rock, the substratum 

 lu-ing in most places Chalk, but between it and the lowest lava- 

 flow there is always a bed of brown ferruginous clay full of flints. 

 These lower lavas are mostly massive or amygdaloidal basalts, and 

 tlu-ir combined thickness is from 400 to 500 feet. 



Between the two series of lavas there is a break which appears 

 to have coincided with the plutonic phase above mentioned, when 

 the intrusive masses of gabbro and granite were formed. In 

 Antrim this is marked by a band of stratified beds consisting of 

 brown and red clays with layers of lignite, beds of pisolitic iron -ore 

 (bauxite), of volcanic sand, and conglomerates composed of pebbles 

 of rhyolite and basalt. Over these beds are piled thick and 

 extensive sheets of basalt and dolerite, which at Sleamish have a 

 thickness of about 600 feet. The well-known columnar basalt 

 at the Giant's Causeway is one of these sheets and overlies a bed 

 of bole or laterite. 



At Glenarm and at Ballypalady near Templepatrick there are 

 thick deposits of iron-ore, the lower bed being a compact ferru- 

 ginous earth known as lithomarge, which is sometimes 40 feet 

 thick, and is overlain by pisolitic ore, and these occur some 600 

 feet from the base, and 400 feet from the top of the basaltic 

 formation. At Glenarm they are associated with sandy clays and 

 pebble beds, which enclose a seam containing well-preserved leaves 

 and plant remains. Among these Daphnogene Kanei, Sequoia 

 . Coutssue, Macclintockia Lyelli, and leaves of Platanus, Quercus, 

 and Rhamnus have been identified by Baily. Mr. J. S. Gardner 

 considers the flora to be of early Eocene age, not Miocene as 

 previously supposed. 11 



Scotland. The basaltic plateau of Ulster is only a portion 

 of a very extensive tract of similar materials which has been 

 largely broken up and destroyed, but must have originally 

 stretched northward to the west coast of Scotland, where other 

 large remnants of it are found in the Isles of Mull, Eigg, Rum, 

 Skye, and Raasey. In the present connection the most important 

 Scottish locality is the promontory of Ardtun Head in the south- 

 western part of Mull. Here beds of gravel sand and shaly clay 

 are intercalated between two great sheets of basalt and have 

 yielded many plant remains. The beds were first investigated by 

 the late Duke of Argyll, but more recently by Mr. J. S. Gardner, 12 

 from whose account the following is taken, together with the 

 illustrative section, Fig. 187. 



The sedimentary rocks appear along the seaward face of the 

 headland for a distance of rather more than a mile, and the 

 succession seen in one of the quarries is as follows : 



