ON THE SUPERFICIAL DEPOSITS OF JERSEY 

 AND GUERNSEY. 



BY ANDREW DUNLOP, M.D., F.G.S. 



During the past few years I have paid some attention to the 

 quarternary geology of Jersey, and it is therefore interesting 

 to me to find that the superficial deposits of Guernsey are 

 being carefully and systematically examined by the Society 

 of Natural Science there. The valuable papers of Messrs. 

 Collenette and Derrick,* and the reports of the Geological 

 Section of the Society show that, as might have been ex- 

 pected, the deposits on the two islands resemble each other 

 closely. In both we have raised beaches at various heights 

 all round the coast, and a few at some distance inland ; in both 

 we have the yellow clay, or brick earth, with its contained 

 rock fragments resting on, or including the raised beaches, 

 and in both we have peat and forest beds extending out under 

 our present shores. 



In Jersey the earliest recognised and best known raised 

 beach is one found at various points all round the island from 

 spring tide high water mark to above ten or fifteen feet above 

 it, that is to say, from twenty to thirty or thirty-five feet 

 above mean tide level, f Our highest raised beach is that at 

 the top of South Hill, an outlying part of the isolated hill on 

 which Fort Regent is built. It lies in a cup-shaped depres- 

 sion, which looks like the section of a gully or pocket, at the 

 top of a cliff formed by a deep cutting. It consists of tightly 

 packed smooth round pebbles of fine red granite, similar to the 

 rock below, with some sub-angular fragments, and it is covered 

 by yellow clay containing numerous angular and sub-angular 

 blocks. 



I had already given the height of this beach as 120 feet 

 above spring tide high water mark,f but I became doubtful 



* Transactions, Guernsey Society of Natural Science, 1892. 



t Owing to the absence of an official datum, the want of a good map giving 

 heights, and the difficulty of getting measurements taken, I am doubtful of the 

 exactitude of many of the levels. 



% " On Raised Beaches and Rolled Stones at High Levels in Jersey." Quarterly 

 Journal Geological Society, November, 1893. 



