The Chalk of Suffolk

From its broad expanses of rolling downlands across southern England, the Late Cretaceous Chalk Group sweeps northwards across much of East Anglia, and on into Lincolnshire and Yorkshire. The Chalk is the major bedrock unit across Suffolk, and dips gently eastwards beneath much of the East Anglia region. The oldest strata are locally exposed along the western margin of the outcrop, for example near Mildenhall, and progressively younger horizons are introduced eastwards towards the coast. Consequently, the Chalk is thickest in the eastern part of the Suffolk region, reaching about 250 m in the Combs Borehole [TM 0427 5625] near Stowmarket; perhaps close to 300 m beneath Ipswich; and about 321 m in a borehole at Lowestoft [TM 5380 9260] (Moorlock et al., 2000). Northwards, boreholes in Norfolk have proved more than 400 m of Chalk at Trunch [TG 2933 3455] (468 m); Somerton [TG 4607 2120] (433 m); and West Somerton [TG 4736 1935] (423 m) (Arthurton et al., 1994), at least part of this increased thickness being attributable to the preservation of younger chalk in the upper parts of these successions. Just as in neighbouring Essex and Norfolk, much of the Suffolk Chalk is buried beneath a variable succession of post- Cretaceous, predominantly Quaternary deposits, but including Palaeogene and Neogene strata in the south-east of the county. For this reason, the region has not developed the typical downland landscape of southern England, and our geological understanding of the Chalk of Suffolk has to be assembled from rare natural exposures, chalk quarries and borehole data.