Vol. 69.] THE AGE OE THE SUFFOLK VALLEYS. 589 



Boulder Clay extends down into the small tributary valleys and 

 sometimes thickens as it does so, being more denuded off the 

 uplands, is brought out very strikingly in course of mapping the 

 ground. The lateral valleys between Ipswich and Needham Market 

 illustrate this point ; and in the valley of the Belstead Brook 

 (south of Ipswich), at Thorrington Hall Crag- pit, Boulder Clay 

 ploughs down into the Pliocene Beds. 



Brett Valley. — At Layham, Hadleigh, and other places 

 northwards to Nedging, similar phenomena are observed. Indeed, 

 the Brett Valley is in many ways a small edition of the Gipping 

 Valley. 



Box Valley. — At Polstead and Boxford in this small valley 

 which runs southwards to the Stour, the Boulder Clay occurs as a 

 valley-deposit. Excellent sections of the very chalky Boulder 

 Clay of West Suffolk were recently exposed at the old Tudor house 

 south-west of Boxford Church. 



Stour Valley. — The classical sections of Sudbury need only be 

 quoted. The Rev. E. Hill is 'inclined to look on them [that is, the 

 beds of Boulder Clay] as deposited on the sides of pre-existing 

 hollows'. 1 



The sands and gravels occurring below this Upper Boulder Clay 

 often behave rather curiously in the valleys of South Suffolk. In 

 many cases they certainly appear to transgress the Eocene outcrops 

 and dip down into the valley, resting in places on the Reading 

 Beds (Whitton) or on the Chalk (Bramford). The difficulty is 

 that here we may be dealing with gravels of two or more different 

 ages. The fact that the gravels often contain much Jurassic debris 

 and many flint-casts of Chalk fossils (low-zonal forms) makes it 

 apparent that they are outwashes from the oncoming Boulder 

 Clay and its ice-sheet. 2 Hence they should rather be classed as 

 Upper Glacial with the Boulder Clay, than as a separate series. 

 The loams which occur lenticularty in them, and are formed as 

 washes from the Boulder Clay, are then easily explicable. 



This evidence from the Upper Glacial deposits goes to prove that 

 the present broad type of valley-system was clearly pre-Upper 

 Boulder Clay in age, and, probably in part also, older than some of 

 the Glacial Sands and Gravels. The rivers, however, appear to 

 cut through the rather different sands and gravels which form so 

 large a part of the Suffolk heathland. 



IV. Evidence oe Age adduced erom Glacial Disturbance 

 in the Valleys. 



The phenomena discussed in this section belong to the valleys of 

 the Aide, Deben, Gipping, Brett, Box, and Stour, but are best 

 exemplified in the Gipping Valley where more work has been 

 done upon them. The last-named valley is comparatively large, 



1 E. Hill, 1912 (34) p. 26. 



2 Mr. Harraer has, I believe, suggested this on other grounds. 



