GEOLOGY 



system, while in lower levels of the present valleys, at Warren Hill east 

 of Mildenhall and Redhill, both derived and contemporary implements 

 are found.* 



The consideration of these old valley deposits is a subject which 

 leads on to that of the origin of the present scenery. 



The main features over great part of England were sculptured 

 prior to the Glacial period. The main features in Suffolk are of subse- 

 quent date. 



Thus the Chalk escarpment in pre-Glacial times may have risen in 

 Suffolk to heights comparable with those now found along the Chiltern 

 Hills, the Dunstable and Royston Downs. It has in any case been 

 considerably planed down, and excepting near Newmarket, where the 

 ground rises to 275 feet, and at Mildenhall, its distinctive features have 

 been obliterated. 



The widespread Glacial Drifts practically overwhelmed the county ; 

 ice-action tended to smooth the inequalities of the land, though here 

 and there a deep trough was excavated ; and the subsequent features 

 have been carved out of the somewhat irregular accumulations of these 

 erratic deposits, and partially out of the underlying strata. 



The melting of the ice led to torrential waters, which marked out 

 some of the earlier valleys,'' and distributed masses of coarse gravel here 

 and there. The erosion of the ground has revealed no traces of the earlier 

 scenery ; indeed, over a great part of the county the thick drifts have not 

 been intersected. Streams flow over them to join the main river courses 

 which have cut deeply into the land. 



Subsequent depression, which took place no doubt slowly, has 

 tended to arrest excavation, and the rivers widen, but, except in the 

 higher courses, no longer deepen their channels. They have become 

 sluggish, and in a few localities the hollows which were formed by 

 estuarine action, or by the serpentine wanderings of the rivers, have been 

 preserved as broads : tracts which are being slowly silted up and narrowed 

 by the growth of marsh plants. Some of the broads, like Fritton Decoy 

 and Oulton Broad, are held up by means of artificial embankments ; 

 others, like those of Easton and Benacre, are barred by recent shingle. 

 Small meres sometimes arise in areas where, owing to dissolution of the 

 Chalk, the ground has subsided below the plane of saturation in that 

 formation, as in the case of Barton Mere. 



The Alluvium, which forms level meadow or marsh land bordering 

 the rivers, is one of the latest deposits, and may be said to be still in 

 process of formation. It comprises deposits of varied character, but 

 mainly silt and clay with peaty layers and gravel, altogether 20 to 30 

 feet in thickness. 



These low-lying tracts occupy a small area in north-western 

 Suffolk, a part of the Bedford Level, itself a portion of the Fenland ; and 

 strips of alluvium fringe the higher courses of the Lark and the Ouse. 



1 Geol. Mag. (1902), p. 105. 



^ See also Rev. O. Fisher, ^mt. Joum. Geol. Sec. xvii. 2. 



27 



