20 DR T. J. JEHU ON 



The following succession can be traced in the deposits : — 



4. Soil and Blown Sand. 



3. Upper Stony Clay. 



2. Sands and Gravels. 



1. Lower greyish-blue or purple Boulder Clay. 



The Upper Stony Clay and the Sands and Gravels form almost the entire cliff". The 

 Lower Boulder Clay only appears at the base of the cliff at one or two places. This 

 Boulder Clay is very tough and homogeneous, being comparatively stoneless. On the 

 surface it has a somewhat reddish or purple hue, but when dug into it has more of a 

 dark greyish -blue colour. It can at times be traced underneath the pebbly foreshore. 



The Sands and Gravels in this mound generally show distinct bedding, and the beds 

 are arched in a curious way and pass under the Upper Stony Till. The gravels and 

 sands contain many flakes and fragments of slate and shale. There are some well- 

 marked beds of bigger water-worn boulders. The sands vary from very fine yellow to 

 coarse grey. The Upper Stony Clay is a true boulder clay, greyish in colour where 

 unweathered, but becoming yellowish and friable on weathering. The included boulders 

 are of varying sizes, and are scattered irregularly throughout the mass. Many of them 

 show well-striated faces. All are subangular or more or less rounded in form and con- 

 sist mostly of Welsh rocks, especially greenstones. The large boulders lying on the 

 beach below have evidently been derived to a great extent from this Upper Till. In 

 places the till tends to become a mass of boulders or coarse gravel. Shells, in a very 

 fragmentary condition, occur rarely in the Upper Clay. The only form recognised was a 

 Turritella. Chalk-flints are readily detected. Among other erratics found were the 

 Ailsa Craig micro-granite, the Goat-Fell (Arran) granite, Dalbeattie granite, schistose 

 and serpentinous rocks, possibly from Anglesey, and a reddish felspar porphyry which 

 may have come from no great distance. 



The Dinas Dinlle mound is separated by a low cliff* consisting entirely of the Upper 

 Till from another mound which occurs a few hundred yards further south in which the 

 cliff sections attain heights of 40 to 50 feet. Here the entire cliff is made up of boulder 

 gravel showing but little trace of stratification. Opposite the centre of the mound the 

 matrix is sandy or gravelly, but towards the two ends it becomes more clayey in 

 nature. 



A diagrammatic section of the mound of Dinas Dinlle is given (fig. 1). 



For about 2\ miles to the south-west of the sections just described the coast 

 is fringed by lowlands, and the sea has thrown up a ridge of shingle just above the 

 high-water line. There have been considerable changes along this part of the coast within 

 recent times, for half a mile out to sea are found submerged the remains of an ancient 

 camp known as Caer-Arianrod, which figures in some of the traditional Welsh stories 

 — the Mabinogion. Cliffs formed by Drift deposits begin to appear again at Point Maen 

 Dulan. At first the cliff is low, but it gradually rises, reaching a height of about 80 feet 



