Vol. 69.] THE AGE OF THE SUFFOLK VALLEYS. 615 



the streams became sluggish, the wide valleys took their present 

 rather sinuous courses. (It is to be noted that the rivers themselves 

 also meander independently through their alluvial flats, ofteu resting 

 upon Drift in the sinuous valleys.) The valleys are of the shallow 

 trough-like type v ' described by I. C. Russell. 1 



Thus, before the oncoming of the district-glaciation, the valley- 

 system had reached -a fairly mature state, and it is possible that 

 had not this develojDment been now arrested, further grading 

 and capture might have resulted. The great outwashes of sand and 

 gravel from the ice-sheets on the north-west spread over East and 

 South-East Suffolk, extending in places down into the valleys, only 

 to be excavated again for the most part by the streams of water 

 from the same source taking advantage of the channels to the sea 

 which the valleys provided. Thus, the fact that the greater number 

 of the valleys are cut through such sand and gravel, but that some- 

 times the deposit flows over into them, would be accounted for. 



The oncoming ice-lobes themselves would take advantage of the 

 hollows already made in the land-surface, and in an attempt to 

 straighten out the winding valleys, would buttress themselves 

 upon and over-ride each successive projecting spur. Upon the 

 'recession of the ice, Boulder Clay was left in all the valleys as well 

 as on the plateau, and was covered by the torrential gravels so well 

 observed in the Suffolk valleys. The high-level glacieluvial gravels 

 also would have been laid down at this time. In fact, it appears 

 that the streams fed by the melting ice were overloaded with 

 detritus, and they deeply filled their valleys with debris, as 

 described by Russell in the glacier-valleys of the Cordilleran 

 region, 2 only, however, to resume the work of excavation and leave 

 the river-terraces and higher-level gravels as evidence of former 

 conditions. It is noteworthy in this connexion that there is a 

 broad development of terrace (a mile and a half wide) at Ipswich, 

 where the valley narrows and takes a sharp bend ; similarly also 

 at Sudbury and Woodbridge. (Hence, no doubt, the early settle- 

 ments and establishment of the various Suffolk towns.) The top 

 of the Gipping terrace roughly follows the 50-foot contour in the 

 lower part of the valley, but rises gradually to the 100-foot contour 

 near Stowmarket : that is, it maintains a fairly constant elevation 

 above the present level of the river. Buried peat and freshwater 

 deposits found in the bed of the Orwell estuary for a length of 

 7 or 8 miles, and outside the Deben estuary, 3 prove a subsidence 

 since Glacial times of at least 30 feet. Mr. Clement Reid states 

 that the submergence amounts to something between 60 and 80 feet, 

 all through East Anglia. 4 From the terrace-levels the subsidence 

 seems to have been general over the area — there is no evidence 

 of tilting — and it is this subsidence which has buried the lower 



» Bussell, 1898 (17) p. 151. 



2 Ibid. pp. 231 & 284 ; see also G-. W. Lamplugh, Q. J. G. S. vol. Ixviii (1912) 

 p. 251 (discussion). 



3 Taylor, 1875 (6) p. 82, and 1882 (9) p. 573. 

 i Reid, 1913 (38) p. 22. 



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