62 W. Swanston — Clays overlying Basalt, Lough Neagh. 



II. — On Supposed Fossiliferous Pliocene Clays overlying 

 Basalt, near the Shore of Lough Neagh. 



By William Swanston, F.G.S., Belfast. 



TN the Geological Magazine for December, 1876, appeared a 

 short paper on certain clay beds near the south-eastern shores of 

 Lough Neagh. The paper is intended to supplement a more extended 

 communication entitled, " On the Age and Mode of Formation of 

 Lough Neagh," read by the same author — Edward T. Hardman, 

 Esq., F.C.S., H. M. Geol. Survey of Ireland— before the British 

 Association in 1874, 1 and also read before the Koyal Geological 

 Society of Ireland in January, 1875. 2 The beds in question are 

 described "as a very extensive and important deposit, spreading 

 (under water and on shore) over an area that cannot be less 

 than 180 square miles in extent, and probably in some places 500 

 feet thick. They repose on the basalt, and are covered by drift. 

 All the evidence we have points to their being of Pliocene age." 

 The author, after giving a sketch of the Geology and Physical 

 Geography of the district, proceeds with a description of the clay 

 beds and associated lignites, and gives abstracts of numerous borings 

 ranging in depth from a few feet to 192 feet, which have been made 

 over this area. These borings disclosed a series of light-grey and 

 variously-coloured plastic clays, containing hard nodules of clay- 

 ironstone inclosing leaf and other plant-remains, also large quantities 

 of black lignite, occurring frequently in masses throughout the beds, 

 but sometimes bedded. 



From the fact that no visible junction was known between the 

 clays and the rocks upon which they repose, much elaborate argument 

 was brought forward to prove that the former were of later date than 

 Miocene, and rested on the surrounding basalt of that age. Hitherto 

 no fossils except plant-remains had been found in them, and, in the 

 absence of more direct evidence, they were considered to be of 

 Pliocene date. The subsequent discovery 3 of fossil shells in a clay 

 band on the banks of the Crumlin Eiver, and which clay band was 

 supposed to rest in this place directly on the basalt, seems to have 

 proved to the satisfaction of the author of the paper, and to Professor 

 Hull, F.E.S., who examined the section at the same time, that the 

 beds were undoubtedly of Pliocene age. 



Owing to the extremely delicate structure of the shells, and the 

 friable nature of the bed in which they occur, it is most difficult to 

 obtain good specimens ; those procured by Mr. Hardman were 

 admittedly in so bad preservation that Mr. W. H. Baily, F.G.S., to 

 whom they were submitted, would not do more than express an 

 opinion regarding them, than that they may possibly belong to a new 

 species. The author, however, seemed to be convinced that they 

 belonged to a species of JJnio, not unlike JJnio Solanderi of the 

 Upper Eocene of Hordwell Cliff, Hampshire ; and is so far satisfied 



1 British Assoc, Trans, of Sections, p. 79. 



2 Journ. Royal Geol. Soc. of Ireland, vol. iv. part iii. new series, p. 170. 



3 Geological Magazine, December, 1876, Decade II. Vol. III. p. 556. 



