Page:VCH Suffolk 1.djvu/35

 GEOLOGY SUFFOLK forms part of the East Anglian plain, and consists almost wholly of an undulating region which rarely attains an elevation of 400 feet. The greater portion of the county rises from 80 to 200 feet above sea-level ; there are no prominent hills, and even the district between Stowmarket and Harleston, to which the term ' High Suffolk ' has sometimes been applied, lies below 200 feet. The highest ground is between Haverhill and Bury St. Edmunds, and this reaches 417 feet at Rede. The great alluvial tract of the Fenland extends to Mildenhall in the north-western portion of the county, and constitutes a lower plain. The main features are those of the river valleys, notably along the lower courses, which widen out into the pleasant estuarine waters of the Deben, Orwell and Stour, or expand — as in the case of the Waveney where it joins the Yare — into the brackish water ' broad ' known as Breydon Water. The coast line is nowhere protected by hard rocks, the cliffs being formed of loose sands, gravels and clays, which yield so readily to the combined attacks of land-springs and sea that the losses have been dis- astrous. The geological structure of Suffolk is comparatively simple. The Chalk forms the foundation of almost the entire county. Its base would be reached just below ihe fens of Mildenhall, and it is inclined gently towards the south-east. Thus at Culford near Bury St. Edmunds it has a thickness of 526 feet ; at Stowmarket and to the south-east it is over 800 feet. It forms part of that shallow trough or syncline known as the ' London Basin,' which in the southern and eastern parts of the county where the Chalk is thickest supports a mass of Eocene strata. These appear at the surface at Sudbury and Ipswich, and have been proved in borings at various places, including Southwold and Lowestoft. Stretching irregularly across the worn surfaces of the Eocene in the southern, and on to the Chalk in the north-eastern parts of the county, are found the several divisions of the Crag formation for which Suffolk is especially famous. Nowhere else in England is there a better hunting- ground for the collector of fossils than that portion of the Crag district which extends from Felixstow to Aldeburgh and inland to Ipswich and Woodbridge. There in many a pit shells and other organic remains in great abundance and variety may at all times be obtained. These richly fossiliferous strata have been partially destroyed and I I I