150 



Proceedings of the Royal Irish Academi/. 



Geological History of the District. 



Late Glacial History . 



With the fluctuations of level ^hich took place in Glacial times 

 we are not directly concerned; but the question of land-level at the 

 close of the Glacial Period hears directly on our subject, as furnishing 

 the starting-point of the series of movements with which we are 

 dealing. The high-level shelly gravels, fossiliferous Eoulder-clays, 

 and eskers of Ireland, which were formerly held to indicate sub- 

 mergence during the Ice Age, are now generally believed by students 

 of Glacial geology to have been formed by the transport of material by 

 land-ice, and by waters flowing on the edges, or in the body of an ice- 

 sheet.^ This view has recently received, in the south of Ireland, 

 strong confirmation in the finding by Muff and AVright- of an early- 

 Glacial raised beach, extending far along the southern coast, and 

 having a level of about 10 feet above that of the present beach. The 

 deposits which rest on this beach, beneath the Eoulder-clay, bear 

 witness that at no time subsequent to their deposition has the land 

 been relatively lower than at present. They point to a rise in the 

 land-level of some 20 feet between the time when the beach was 

 formed and the deposition of the Eoulder-clay. This Glacial emer- 

 gence of the land would appear to be a widely recognized feature 

 in the Eritish Islands, and may have been of considerable amount. 

 It lasted on into post-Glacial times, as witnessed by the steady 

 cutting down of the river-valleys during that period, and was 

 succeeded by a widespread late post-Glacial submergence of some- 

 what less amount, which in the southern portion of the Eritish 

 Islands left the country as we now find it. "\V. Pengelly^ estimated 

 the emergence on the south coast of England at 70 feet or more, the 

 subsequent submergence at at least 40 feet. In the north of Ireland, 

 this high land-level, without doubt, continued till after the growth of 

 the deep peat-bed of the Eelfast estuary, which postulates a level at 



^ See G. W. Lamplugh and others: "The Geology of the country around 

 Dublin," 1903, pp. 45-48 ; and "The Geology of the country around Belfast," 

 1904, pp. 59-65. (Memoirs Geol. Survey, Ireland.) 



~ H. B. Muff and W. B. Wright: " On a Pre-Glacial or Glacial Kaised Beach 

 in County Cork." Geol. Mag. (4) x., pp. 501-503. 1903. 



^ Trans. Devon Assoc., vol. i., part iv., p. 34, 1865 ; and vol. ii., pp. 25, 134. 

 1867. 



