556 E. T. Hardman — Fossiliferous Pliocene Clays. 



V. — Fossiliferous Pliocene Clays oveelting Basalt, near the 



Shore of Lough Neagh. 



By Edward T. Hardman, F.C.S. ; H.M. Geol. Surv., Ireland. 



(PLATE XXII.) 



IN the Eeport of tlie British Association for 1874^' will be found 

 the abstract of a paper on the Age and Mode of Formation of 

 Lough Neagh, with a description of the Pliocene clays which form an 

 ancient and extensive delta at its southern extremity. At the time 

 I penned the paper in question, although I was perfectly satisfied 

 from cumulative circumstantial evidence that the clays were of much 

 more recent date than the Miocene Basalt which surrounds the lake 

 on three sides, I had no actual proof to bring forward — the junction 

 of the basalt and the clay beds being nowhere visible, so far as I had 

 had an opportunity of examining the district, this comprising all the 

 shores of the Lough, with the exception of a small corner near 

 Crumlin ; and it was therefore necessary to state, even at the risk of 

 tediousness, the reasons why the clays must be considered to be the 

 uppermost, and to be of Pliocene age. 



During a recent visit to this hitherto unexplored locality, ac- 

 companying Professor Hull, for the purpose of tracing the eastern 

 boundaries of these beds, we were so fortunate as to meet with a 

 well-exposed section, showing the clays resting on a denuded 

 surface of basalt. This was a pleasant encounter. At the same 

 time, one could hardly help a slight feeling of regret that so much 

 elaborate argument had been already in a manner ••' fooled away," 

 as Mark Twain has it — to prove what was here a self-evident fact, 

 had one but seen it in time. We were also so lucky as to find at 

 this place the only fossils which, with the exception of plants,, have 

 yet been discovered in the Lough Neagh clays. 



It may be well to mention that these beds form a very extensive 

 and important deposit, spreading (under water and on shore) over 

 an area that cannot be less than 180 square miles^ and probably in 

 some places about 500 feet thick. They repose on the basalt, and 

 are covered by drifts All the evidence we have points to their 

 being of Pliocene Age. 



The locality where the particular beds I propose to describe now are 

 found is on the Crumlin River, about a mile from the eastern shore 

 of the Lough, and about 2J miles from Crumlin village. The basalt 

 is exposed for some distance along the stream, and following it 

 downwards we came upon the following section : — 



Section in Crumlin Eiveb.^ 



A. Eiver Gravel and Alluvium 



Dark Grey Laminated Sandy Clay 



/. „ ,, ,y full of JJnio-Wke skells ... 



Dark Grey Clay 



m. Coarse Gravelly Clay — pebbles of quartz and basalt — resting in 

 pockets and erosions of basalt 



B. Modular Zeolitic Basalt, greatly eroded 



28 

 This section is exposed for about 40 yards. The clays are visible 

 for some distance lower down, and in one place exhibit very well 

 ' Trans, of Sections, p. 79. 2 gee PI. XXII. Fig. 1. 



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