C— GEOLOGY 8 1 



Maney near Sutton Coldfield provide two examples where it is a question 

 of distinguishing between a Main Irish Sea and a Welsh origin ; whereas 

 the drifts of the Ridgeway in East Worcestershire seem to be compounded 

 of Welsh and Eastern elements. This long ridge, ranging in height 

 from 550 CD. in the north to 350 CD. in the south, bounds the Arrow 

 valley on the west. It is capped for a distance of 11 or 12 miles from 

 near Blackwell to 3 miles south-west of Alcester by a narrow outcrop 

 of sands, gravels and boulder clays. In its northern part a few Irish Sea 

 erratics occur in the clay, but farther south there have been found at 

 Crabbs Cross an Oxford Clay ammonite {Gulielmiceras) ; and at Weethley 

 flints and a Leicestershire granophyre, all indicating that some of its 

 material came from the north-east. As the Ridgeway lies outside the 

 region of those well-developed Eastern drifts, whose distribution in the 

 Avon valley has been described by Dr. Tomlinson in 1935, two explana- 

 tions appear possible. Either its eastern elements are relics of a very 

 early Eastern glaciation or they provide a record of a temporary advance 

 of the Main Eastern glacier down the Avon, perhaps as far as Tewkesbury, 

 during which a side-lobe was thrust up the Arrow valley. Other evidence 

 in favour of this latter view is the presence of flint-bearing deposits 

 resembling boulder clay at Harvington (Tomlinson), at Evesham (Dines), 

 at Besford, and on top of the Bushley Green Terrace deposits at Bushley 

 and Apperley near Tewkesbury. For these reasons I have on Fig. 2 

 adopted the latter explanation, though I realise the slender nature of 

 the evidence. 



Over much of that part of the Warwickshire-Staffordshire Plateau 

 which is drained by the upper waters of the Tame, Cole and Blythe, the 

 mantle of drift is comparatively intact, and frequently forms the valley 

 floors ; but on the Severn- Avon side of the watershed of England it becomes 

 very ragged, projecting outwards as promontories or forming outliers on 

 the highest hills (Figs, i and 4). As we go towards the Severn and Avon 

 these outliers become less frequent and usually smaller, and in some cases 

 a mere skin of pebbles is all that remains. Doubtless the large isolated 

 boulders sometimes met with in otherwise drift-free areas, represent the 

 final fate of such high level drifts. 



That the highest points are surmounted by drift is so far a rule that one 

 is forced to view the capping as remnants of a more or less continuous 

 sheet which once stretched far into the vales of Severn and Avon. Here 

 it has in most places been completely destroyed. Evidence of its presence 

 must be sought for on the hill-tops and not in the valleys, all of which in 

 their present state are younger than the glaciation. This statement 

 perhaps needs qualification, for fluvio-glacial deposits occur at fairly low 

 levels near the Piddle Brook and in the Salwarpe and Stour valleys. 

 These, however, appear to belong to the waning phases of the glaciers 

 when the lower parts of the vales, freed from ice, had become subjected 

 to river erosion. The new valley floors thus formed then received 

 deposits from the glaciers which still occupied the country further 

 north. 



It is, I think, fair to conclude that the ice sheets at their maxima occu- 

 pied the vales, and that these were far shallower then than now. This 



