70 Dr. Woolacott — A Raised BeacJi in Durhain. 



has suggested the possibility that it may be the remnant of an 

 Interglacial (or Glaciation-Interval) beach, preserved in a similar 

 way. I am unable to accept either of these hypotheses. The points 

 definitely against them are (1) the fauna is a recent temperate one — 

 there are apparently no species characteristic of Arctic conditions, 

 (2) pebbles of Lake District, Cheviot, and Firth of Forth rocks 

 occur in the deposit, (3) it is not overlaid by true boulder clay bat 

 by reasserted boulder clay, (4) it is impossible to isolate the part of 

 of the beds that is allowed by everyone to be a littoral deposit, from 

 that which is conjectured to be Fluvio-glacial, (5) since the top 

 of the course of calcreted gravels is regular and persistent (even 

 if we assume the rest of the beach has been removed by ice) we should 

 have to admit that the Fluvio-glacial beds are forming a kind of 

 pseudomorph of the beach for some miles, and maintaining a uniform 

 level, whether the platform is Magnesian Limestone or boulder clay. 

 It would appear impossible, if the whole of the beach were removed, 

 that the platform of boulder clay would not have been destroyed by 

 the conjectured ice-movement, and highly improbable that the top 

 of the Fluvio-glacial gravels that replaced the beach could always 

 m.aintain a uniform level for such a long distance. 



One of the objections raised some years ago against the occurrence 

 of late-Glacial or Post-glacial Eaised Beaches on the Durham coast, 

 was that it had been found impossible to trace them in Yorkshire,^ 

 and another that there was a considerable stretch of country to the 

 north from which marine deposits of this age are apparently absent.^ 

 One of the causes of this may be that they are in reality late-glacial 

 and that although the Durham littoral was free from ice when they 

 were forming, yet it was still occupying part of the coast of north- 

 east England, while another is that the uplift was not a uniform one. 

 I further think that the great amount of coastal denudation and 

 reassortment of glacial material along the main rivers that has taken 

 place since the end of the Ice Age is not appreciated by all geologists. 

 From parts of the coast (e.g. north-east Yorkshire) the beaches may 

 have been removed by denudation of the superficial deposits that 

 once covered this coast as with a mantle. It is of interest in connexion 

 with this subject that late Pleistocene raised marine shore-lines 

 passing into river terraces do occur up to about 125 feet in the 

 Firths of Forth, Clyde, Tay, and elsewhere in Scotland,^ and that an 



^ The estuarine leafy clays and well-worn shingle which occur at Kirmington 

 (Lincohishire) obviously lessens the force of this argument (see footnote p. 71). 



'^ Low level beaches (30 feet (?) and 10 feet) do occur in North Northumber- 

 land, and high level beaches (125 feet) occur in Scotland. 



3 In these deposits fossils are scarce, but the shells found ia connexion with 

 the higher beds indicate a colder climate than those of the Durham beaches. 

 The fauna includes Pecten greenlandicus, Leda arctica, Tellina myopsis (all 

 Arctic forms) and remains of the small Arctic seal. The lower terrace is 

 associated with clays containing Scrobicularia jiijjerata (which also occurs in 

 the Kirmington deposit), and indicates the incoming of warmer conditions. 

 J. Geikie, Great Ice Age, p. 273, and Geol. Surv. Mem. : " The Neighbourhood 

 of Edinburgh," 1910, p. 335. 



