Vol. 69.] AGE OF THE SUFFOLK VALLEYS. 613 



The Drift-deposits (Upper Boulder Clay and at times Glacial 

 Sand and Gravel) lie in the subsequent and consequeut portions of 

 the valleys alike. Where these valleys are winding in character, 

 the sinuosity must have been developed before the oncoming of 

 the Upper or Great Chalky Boulder Clay. It is quite evident that 

 the small streams meandering in these wide valleys at the present 

 time cannot have carved out such features. 1 The present rivers, as 

 insisted on frequently by Mr. E. W. Harmer with especial reference 

 to Norfolk, 2 are out of all proportion to the valleys which they 

 occupy. We have seen that such valleys are certainly either pre- 

 Glacial or early Glacial in age. When, then, was this somewhat 

 mature, low-graded system developed? During the Pliocene Period, 

 the tectonic wave-like movements of the land that now forms 

 East Anglia resulted in a gradual rise southwards and depres- 

 sion northwards, and were doubtless adjustments following the 

 strong Miocene folding of the South of England and the Continent. 

 Reasoning from the boulders found in the Red Crag (London Clay 

 debris, Hertfordshire puddingstone, sarsens, Chalk-flints, masses of 

 Kellaways Rock crowded with Rhyndhonella socicdis, other Jurassic 

 rocks, Bunter pebbles, granites, etc.) the drainage seems to have 

 been towards the east; but, at the end of the Crag Epoch, the 

 drainage appears to have been towards the north or north-west, if 

 we are to believe the Continental geologists, who see in the mica 

 with which the ' Chillesford-Clay river ' is loaded, material derived 

 from the Ardennes or even farther south. 3 The Butley, Aide, and 

 more northerly rivers cut through these Chillesfordian Beds : 

 therefore, the present valley-system must have been developed in a 

 doubtless long period, which intervened between the Chillesfordian 

 age and the time when the Glacial Sands and Gravels which lie 

 beneath the Upper Boulder Clay were deposited. 



As Prof. J. W. Gregory, Mr. Jukes-Browne, and others have 

 pointed out,* the country at the close of Pliocene time must 

 have had an appearance very similar to that which it now presents. 

 The Cretaceous escarpment had by then retreated almost to the 

 position which it now occupies, and was a well-marked feature, 

 as illustrated by the manner in which the Glacial deposits 

 were banked against its front. 5 The outlines of the present 

 drainage would at this time have been etched upon the south- 

 eastward sloping peneplane. Increasing in power, the rivers 

 graded their valleys and some amount of capture may have taken 

 place, possibly behind a secondary Eocene escarpment. Vertical 

 corrasion gave place to lateral corrasion, and the rivers developed 

 their present wide and open valleys (see fig. 5, p. 614), and as 



1 The average annual rainfall of Suffolk for 1862-1902 was 24'5 inches. 



2 Harmer, 1909 (25) pp. 121 et seqg. 



3 Harmer, 1902 (19) p. 447 ; but see also C. Eeicl, ' Pliocene Deposits of 

 Britain ' Mem. Geol. Surv. 1890, p. 189. 



4 Gregory, 1894 (14) p. 102 ; Jukes-Browne, 1911 (31) p. 428 (also earlier 

 works). 



5 See also Harmer, 1909 (25) p. 114, etc. 



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