[ 446 ] 

 XL VII. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 

 [Continued from vol. xxix. p. 843.] 



February 3rd, 1915. — Dr. A. Smith Woodward, E.K.S., President, 

 in the Chair. 



r PHE following communications were read : — 



1. ' On the Gravels of East Anglia.' By Prof. T. McKenny 

 Hughes, M.A., F.K.S., F.G.S. 



The author discusses the sources from which the subangular 

 gravels that cover such large areas in East Anglia can have been 

 derived. 



He points out that their great variety of fracture, colour, etc. 

 proves that they cannot have come directly from the Chalk, nor 

 from Boulder Clay derived directly from the Chalk, nor from the 

 Lower London Tertiaries, none of which contain subangular gravels 

 but only beds of pebbles, and those mostly of small size. 



The character of the flints in the gravels indicates that they have 

 been derived from surface-soils which have been winnowed and 

 shifted by soil-creep, rain, and streams, until arrested on the terraces 

 and flats of the valleys. 



The dry land of Miocene age was the first over which the flints, 

 of our gravel-beds could have received that subaerial treatment which 

 they all seem to have undergone. There was then no Boulder Clay 

 to protect and obscure the Chalk-with-Elints. 



Then came the submergence which let in the Crag Sea. This, 

 rapidly invaded the land, not giving time to reduce the flints to 

 pebbles but burying remains of animals and plants in coarse sub- 

 angular gravel. In time the subsidence affected more distant 

 shores, and compensating rises of mountain-regions far away began 

 to modify climatal conditions ; ice floated southwards, stranding at 

 various depths according to size, ploughed up and crumpled the 

 shore -deposits, and dropped masses of far-transported material. 

 It is not difficult to distinguish the old shore -deposits, even when 

 they have been crumpled up, from the foreign material introduced 

 by the floating ice. 



When the land had sunk so low that the wind- and tide-waves, 

 could not sort the material, it remained, as brought, a boulder-clay, 

 which is therefore widely spread over the peneplain of the East 

 Anglian heights, and is generally above the gravel and sand of the 

 advancing sea. 



Where the sea was able to work longer at pounding and rolling 

 the flints, immense beds of pebbly shingle or of sand are the result.. 



The Plateau Gravel is traced from section to section across the 

 country, and the characteristics by which it can be recognized are- 

 pointed out. 



