310 D. Woolacott — Sa^ids and Gravels with Marine Shells. 



to be two ways in which this could have been done. It could either 

 have been pushed inland by the ice and deposited at a higher level/ 

 or there is the possibility of it being lifted up from the bed of the 

 sea and carried forward as suggested by Debenham.^) Its 

 regularly bedded and undisturbed nature and its extent are entirely 

 against the idea that it has been carried by ice and dumped down 

 in the place in which it occurs. On the other hand, the evidence is 

 certainly in favour of it having been deposited in place by water ; 

 indeed, it would appear to have been formed as a marginal deposit. 

 The other possible mode of formation is, therefore, that it was 

 formed on the edge of a glacier-lake held up by ice lying off the 

 Durham coast near the end of the G-lacial Period, and that it thus 

 consists of glacial material carried inland and afterwards re-assorted 

 by water on the margin of an ice-dammed lake. The unbroken 

 nature of the shells and their variety are strongly against this 

 view.^ No transported glacial material from the bed of the 

 North Sea with such a varied fauna is known to exist in Durham.^ 

 From the Sheraton Kaims, which occur a few miles to the 

 south and are about 4 miles inland at an elevation of 400 feet, 

 Dr. Trechmann, after careful searching, has only been able to 

 collect some very broken fragments of Cyprina islandica, Mactra, 

 and Turritella ^ ; yet in this deposit whole well-preserved shells of 

 Littorina, Patella, Saxicava, and Purpura occur. 



This deposit and the associated sands and gravels on the Durham 

 coast are therefore of special interest. If they are raised beaches 

 they obviously raise a peculiar question regarding the nature of 

 the uplift that produced them, and if they are not they show how 

 deceptive the evidence obtained from the mode of occurrence of 

 deposits may often be, and they suggest a query regarding the extent 

 of the glacier-lake of which they are the marginal deposits. All 

 geologists to whom I have shown the sands and gravels at Easington, 

 including some who doubted the existence of raised beaches on the 

 Durham coast, regard them as being of direct margin origin, or 

 admit that the deposit is masquerading as an uplifted marginal 

 marine formation. Certainly geologists who described these 

 superficial deposits on the Durham coast as raised beaches would 

 appear to have been justified. Now that a fairly complete record 

 of the glacial deposits of this coast has been worked out it appears of 

 importance that the mode of origin of these particular formations 

 should be determined. They can be much more clearly examined at 



^ Deposits have been observed raised from the sea bed in Spitsbergen by 

 Garwood, Gregory, and Lamplugh. 



^ Quart. Journ. Geol. Soc, vol. Ixxv, 1920. 



^ It is admitted that shell-bearing gravels have been transported inland in 

 County Durham. The question at issue is whether there has been an uplift of 

 the coastal area of Durham since Glacial times. 



^ I have not seen any Patella in place on the rock shelf, although some 

 appeared to have been attached to the large pebbles in the gravel. 



* Quart. Journ. Geol. Soc, vol. Ixxi, 1915, p. 74. 



