CHAP. XII.] ICENIAN PERIOD. 245 



Scaldisien sands being overlain by 528 feet of Pleistocene 

 deposits and underlain by over 400 feet of Older Pliocene 

 sands. 



The highest and latest Pliocene beds known to occur on 

 the borders of the North Sea are those seen on the coast 

 of Norfolk, and known respectively as the Forest Bed and 

 the Leda myalls Bed. The so-called Forest Bed is really a 

 set of beds very variable in composition, comprising layers 

 of sand, gravel, clay, and lignite, with a total thickness of 

 10 to 20 feet ; they contain numerous drifted stumps and 

 branches of trees, with fir-cones and other plant remains, 

 bones and teeth of many mammalia, and estuarine inol- 

 lusca. Its upper surface, however, does in many places 

 present the appearance of an actual land surface, being 

 weathered into a soil and penetrated by rootlets ; here and 

 there also it is covered by lacustrine deposits containing 

 freshwater shells and bones of beavers, mice, moles, and 

 other small creatures. A rootlet bed similar to that of 

 Norfolk, and believed to be of the same age, occurs also at 

 Hopton, Gorton, and Kessingland in Suffolk, so that simi- 

 lar conditions appear to have prevailed over an area which 

 measured at least 40 or 50 miles from south to north. 

 They do not, however, extend far inland, and the neigh- 

 bourhood of Norwich appears to have been comparatively 

 high ground at the time of their formation. 1 



The beds which underlie this terrestrial surface are clearly 

 such as would be formed in the estuary of a large river, 

 and it is therefore reasonable to regard the gravels and 

 sands as river-borne detritus, and to look to the pebbles 

 composing them as affording a guide to the direction from 

 which the river came. These pebbles have been carefully 

 studied by Mr. Clement Reid ; they consist chiefly of flints 

 and light-coloured quartzites, with other stones which seem 



1 Clement Keid, " Geology of the Country around Cromer," p. 55. 



