The oldest rocks exposed at the surface in Suffolk are the mudstones and sandstones of the Gault and Upper Greensand formations which are to be found only in the extreme northwest of the county west of Lakenheath.
There are isolated pockets of Palaeocene sands and clays north of Ipswich and between there and Sudbury to the west.
The clays of the early Eocene Harwich Formation are widespread in the southeast of the county between Sudbury and Orford Ness.
From Bury St Edmunds and Sudbury eastwards the Chalk is overlain by an extensive spread of Pliocene to Pleistocene age 'crag' stretching to the North Sea coast.
Estuarine and marine alluvium is spread across the eastern coastal zone whilst at the other side of the county areas of peat and lake clays, silts and sands occur.