1915. 



Revicivs. 



57 



REVIEWS. 



THE WEXFORD GRAVELS. 



The Wexford Gravels and their bearing on Inter-glacial Geology. By 



Grenvili.e a. J. Cole, M.R.I. A., F.G.S., and T. Hallissy, M.R.I. A., 

 Geological Survey of Ireland. [Extracted from the Geological 

 Magazine (Decade VI.), Vol. I., n. C05, pp. 498-509, November, 1914.] 



The Wexford Gravels have been the subject of considerable contro- 

 versy, much of which appears to have arisen from the efforts made by 

 geologists to fit in the facts of the Wexford area with theories advanced 

 to explain the geology of other parts of the British Isles. Regarding the 

 disputed succession of the deposits in the field, the views put forward 

 by the authors may be accepted as final — that the widely spread and highly 

 calcareous " Marl" is the moraine profonde of the Irish Sea glacier, and 

 the " Wexford Gravels" which occur sporadically in the district are de- 

 rived from this underlying Boulder -clay. The'se gravels in addition to the 

 northern erratics and shells usually found in east coast Glacial deposits 

 contain considerable quantities of chalk -flints, lignite. Pliocene mollusca, 

 &c., apparently derived from the submarine Cretaceous and Tertiary 

 outliers off the eastern and southern coasts. The main purpose of the 

 paper is, however, the bearing on interglacial geology of the Wexford 

 Gravels, and here the authors are on much more debatable ground. 

 It must be admitted that until late in the last century interglacial periods 

 were used in a very casual way by many geologists, the undoubted inter- 

 glacial deposits in alpine lands, and an assumed extensive submergence 

 in the British Isles giving much support to the theory. Active scepticism 

 regarding interglacial land -deposits on the one hand, and the disappearance 

 of the submergence theory on the other has in recent years reduced inter- 

 glacial periods to a rather precarious position — that is in the older sense 

 of an introduction of a fairly complete flora and fauna to these islands 

 during the period. The work of our authors on the Wexford deposits, 

 valuable on so many other points, cannot be said seriously to modify the 

 normal succession of Glacial deposits. The advance of an ice -sheet 

 laying down Boulder -clay — the denudation of this Boulder -clay resulting 

 in the formation of gravels in favourable localities — and the re -advance of 

 ice, usually local ice, depositing a loose stony loam, is a succession very 

 commonly found in Ireland, and this succession may be apj^lied to the 

 W^exford deposits without straining the facts unduly. It may be that 

 our authors regard the lapse of time between the retreat of the Irish Sea 

 ice and the advance of the local ice as an interglacial period. 

 If this is their idea of an interglacial period they may 

 certainly be considered to have made a good case, but in view of the 

 meaning usually attached to the term, recession and re-ad\'ance of the 

 ice would appear much safer expressions. 



J. De W. H, 



