A HISTORY OF WORCESTERSHIRE 



that the fragments of marine shells at these localities are in some, if not 

 all, cases derived from older Glacial gravels, together with many quartz- 

 ite pebbles and derived Jurassic fossils. 



In 1836, Murchison, from the evidences afforded by the recent 

 species of mollusca, suggested ' that the sea must at the time have covered 

 the valley of the Severn from Bridgnorth to the Bristol Channel, thus 

 separating Wales and Siluria on one side from England on the other.' ^ 

 Later on the vievv^ of ' The Ancient Straits of Malvern ' formed the theme 

 of an essay by James Buckman.^ 



Prestwich, in 1892, remarked: 'There can be little doubt that the 

 sea of the Raised Beach period stretched northw^ard up the Valley of the 

 Severn ; but whether it formed a deep bay or estuary, or whether at that 

 time it was prolonged through to the Irish Channel, forming the " Severn 

 Straits " of Murchison, seems uncertain. It is probable that the marine 

 beds at the higher levels should be referred to an earlier stage of the 

 Glacial period.' ^ Mr. W. J. Harrison, however, considers that these 

 recent marine shells were originally derived from a lobe of the ' Irish 

 Sea Glacier ' which invaded Shropshire, and which had scraped up the 

 shells from the bed of the Irish Sea.^ Be this as it may, we can still re- 

 gard those shell-fragments which we find with the mammoth in the 

 valley drifts as having been redistributed from earlier Drift deposits. 



The district, however, is of considerable interest as being on the 

 borders of the large region which was mantled by the ice-sheet during 

 the accumulation of the Great Chalky Boulder Clay of the midland and 

 eastern counties, and which was not affected by any marked glaciation 

 during the later phases of the Glacial period. 



The southern limits of the Boulder Clay must be sought to the 

 north of Bredon Hill, the evidences of the ice action being discernible 

 here and there in the Vale of Evesham and in the vale at Aston Magna 

 and Mickleton, where Boulder Clay was observed in 1853 by G. E. 

 Gavey.^ At the time Mr. R. F. Tomes obtained glaciated Chalk from 

 this Drift. In connection with the discovery, it is interesting to note 

 that pebbles of hard red and white Chalk were found by Buckland in 

 1 82 1, to the south-east of Shipston-on-Stour. 



' Modified Drifts,' in the form of thin scattered drifts with quartzite 

 pebbles, and of valley gravels and loams, succeeded the Boulder Clay, or 

 the melting of the ice which brought it ; and these deposits appear to 

 merge into the old alluvial, and, perhaps in part, estuarine deposits of 

 the great Severn Valley. 



That the Cotteswolds themselves have not been glaciated, is shown 

 by the thick accumulations of oolitic rubble which flank their slopes. 



' Proc. Geo/. Soc, vol. ii. p. 334. 



^ 8vo, London [1849] > see also W. S. Symonds, The Severn Straits, Svo, Tewkesbury, 



1884, and E. Witchell, Prcc. Cotteswold Club, vol. iv. p. 216. 



' Quart. Journ. Gecl. Soc, vol. xlviii. p. 287. 



* Proc. Geo/. Aisoc, vol. xv. p. 404. 



* Quart. Journ. Geo/. Soc., vol. ix. p. 29 ; see also S. V. Wood, Jun., ihid. vol. xxxvi. 

 p. 483 ; and H. B. Woodward, Geo/. Mag. for 1897, p. 485. 



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