232 7 he Irish Naturalist. November, 



A I.ATK GI.ACIAL CLAY AT TEMP^KOGUE, 



CO. DUBLIN. 



BY PROF. GRENVII.I.K A. J. COT.K, M.R.I.A , F.G-S., 

 Director of the Geological Surve.v of Ireland. 



During the work of the Geological Survej' near Belfast 

 several deposits of stratified drift were observed, principally on 

 the lower ground, and these are described in the Memoir^ on 

 that district, issued in 1904. The fine laminated clays of the 

 Lagan valley are dealt with by Mr. G. W. Lamplugh under 

 the name of " warp " clays, a term borrowed from the English 

 fenlands ; and on p. 63 of the Memoir he shows how they 

 accumulated in a lake during the gradual retreat of the inland 

 ice, and while the Scottish ice still occupied the basin of the 

 sea. Prof. James Geikie^ describes fluviatile clays as over- 

 lying the tj^pical estuarine deposits of the Scottish carses, and 

 remarks that "the fine tenacious brick-clays, and even the 

 less cohesive silty or loamy clays, cannot be likened to the 

 dark sludge and mud which now gathers in our estuaries. 

 They in some measure resemble the laminated clays of the 

 loo-ft. terrace. The rivers that flowed into our estuaries 

 whilst the Carse-deposits were being accumulated must have 

 been abundantly charged with the ' flour of rocks ' and finely 

 levigated material." Prof. Geikie uses the character of these 

 later Carse-clays as an argument in favour of a fresh extension 

 of glacial action. It is clear that the glacial sands and gravels, 

 particularly those grouped together to form eskers, result 

 from the washing of material that might otherwise have been 

 dumped down upon the land as boulder-clay. It is clear also 

 that the fine sand and clay thus removed from round the 

 stones must have been carried away to some other area. Now 

 and then these materials are found in estuaries, deposited at 

 some distance from the melting ice, as in the Scottish carses; 

 and now and then they are laid down quietly in glacial lakes, 

 as in the Lagan valle}^ near Belfast. 



Laminated glacial clays do not seem to have been widel}^ 

 observed during the work of the Geological Survey in the 



^ p. 50, &c., and Plate v. 



- " Great Ice Age," 3rd ed., 1894, p. 311. 



