596 MR. P. G. H. BOSWELL ON THE [Dec. 1913, 



small quantity, as, for example, at Barking and Stowmarket, etc. 

 The occurrence of this large quantity of chalky material is clearly 

 ■due to the higher level of the Chalk surface hereabouts, its re- 

 latively greater area of outcrop, and thinner overburden of Eocene 

 and Crag deposits. It seems probable that the absence of any 

 notable thickness of London Clay has in no small degree modified 

 the nature of the disturbances. Some contortion and minor faulting 

 of the silts at higher levels is doubtless due to slipping on the 

 valley-slopes, as explained by the llev. E. Hill in his clear and 

 accurate description of the Sudbury Glacial sections x ; but it seems 

 to me quite probable that some of the disturbance on the Sudbury 

 Town spur, and on the Ballingdon Grove spur on the opposite 

 bank, may be due to buttressing upon them. Contortion, inversion, 

 and buttressing of the beds are to be seen, and mapping on a large 

 scale might throw light on the matter. 



In the brickfield situated on the spurs a mile west-south-west 

 of Little Cornard Church, occur good exposures of bedded silts 

 and chalky sands completely enclosing huge boulders of altered or 

 redeposited Chalk. Their appearance at once recalls the Cromer 

 and Norfolk coast Chalk-masses, as was observed by Mr. Hill, 2 

 who points out the narrowing of the valley here, aud suggests 

 that the great boulders of remanie Chalk were stranded in their 

 present position. I am compelled to agree entirely with this 

 view, and it is interesting to draw attention to the form of the 

 valley immediately above these spurs projecting from the plateau 

 (PI. LV, fig. 3). The 100-foot contour is here thrown back into 

 a bay-like form, and a tract of absolutely flat country a mile 

 long and nearly as broad occurs. In this embayment the slope 

 from the 100- and 200-foot contours to the river is not gradual, 

 but is the normal gradient of the valley-flanks near by, reaching 

 river-level immediately west of the 100-foot contour. This 

 •comparatively extensive flat plain is in many parts liable to 

 floods, and is traversed by ditches and small streams which drain it. 

 It is largely covered by alluvium, but loam and gravel were 

 -also mapped. There seems little doubt that here the Stour in 

 pre-Glacial or early Glacial times made a big bend similar to 

 those in the upper part of its course ; but eventually (perhaps in 

 consequence of increased volume due to the melting of the Upper 

 Boulder-Clay ice), it cut off this bend, and took its present direct 

 course, producing a flat river-formed plain and an oxbow channel 

 which has been silted up. The meniscus-shaped outcrops of loam 

 and valley-gravel mapped by the officers of the Geological Survey 

 bear out this view. (Compare the Sproughton spur in the 

 Gipping Valley, p. 592.) 



In the investigation of these disturbances due to glacial action 

 (many of them on a considerable scale), every example of contor- 

 tion and displacement recorded or observed in the county is found 



1 E. Hill, 1912 (34) p. 27. 



2 Ibid. p. 28. 



