THE GLACIAL DEPOSITS OF WESTERN CARNARVONSHIRE. 21 



half a mile to the north of Clynnog. It is only here and there that good clean ex- 

 posures are displayed. Often the cliff face is obscured by slipping or by overgrowth. 

 Good exposures are seen just to the north of Clynnog, and again opposite the village. 

 These show that the entire cliff in this region is made up of a greyish till weathering 

 yellow, and full of boulders of all sizes. The till encloses lenticular patches of rather 

 fine gravel. The deposit is unstratified, but the boulders often become more numerous 

 towards the top. The beach below is strewn with big boulders which have fallen from 

 the cliff. Shell-fragments occur rarely, but those obtained were too fragmentary for 

 identification. 



This Stony Clay represents the Upper Boulder Clay, and is here of unknown thickness, 

 for the bottom is not reached in the sections. Far- travelled boulders are not uncommon, 

 and the following were obtained from the cliff near Clynnog : — A foliated granite identical 

 with that forming the eastern margin of the Criffel mass in the south-west of Scotland, 

 Dalbeattie granite, the Goat-Fell granite of Arran, the Mull of Galloway granite, chalk- 



so// and 



blown sand 



Up ^~ 



7^ clay Upper Boulder Clay »»*»**»* bJSTclJ ™* aZtj^'td Upper B^Mr Clay 



Fig. 1. — Diagram of the Cliff Section at Dinas Dinlle. 



flints, Carboniferous Limestone showing crinoid stems, and various schistose and serpen- 

 tinous rocks which are probably derived from Anglesey. 



To the south-west of Clynnog the cliffs are again much grassed over or obscured by 

 talus. The heights vary up to 80 or 90 feet. Where best seen the section shows — 



2. Upper Stony Clay — 10 to 12 feet. 



1. Gravels, bedded in places — 60 to 70 feet. 



The bottom of the Gravels is not reached in the section. A little further west fine 

 brownish sand is seen mingled with the gravelly material, which is also finer here. 



At Aberafon, on the left side of the stream, near its mouth, the cliff is over 100 feet 

 high. It is mostly grassed over, but at one place it can be seen to consist of well- 

 stratified sands and fine gravel. There are some gritty beds, but the finer sands are 

 stoneless. In the sands occur pieces of a carbonaceous material resembling coal. 

 Above the gravels and sands and forming the top of the cliff is a clay full of boulders 

 and rounded stones. Mr Mel lard Reade * states that he saw a red clay at the base of 

 the cliff underlying the Sands and Gravels. This was not exposed when the writer 

 visited the spot, probably owing to the slipping of material from above and to over- 

 growth. In the gravels of this cliff a pebble of the Ailsa Craig micro-granite was 

 found. 



* Proc. Liverpool Geol. Soc, vol. vii. (1893), p. 43. 



