GEOLOGY The Upper Chalk, consisting of chalk with nodular and tabular flints, underlies the greater part of Suffolk, from Haverhill through Bury St. Edmunds to Brandon, and in the country to the east, where however it is so much obscured by Glacial drift and Tertiary strata that it appears seldom at the surface and few fossils have been recorded. Chalk with Micraster occurs at Bury St. Edmunds and onwards, probably to Ixworth, Fakenham and Euston Park. At Great Horringer it has been extensively excavated in subterranean workings or galleries. The Marsupite zone probably extends through the country from near Wickhambrook to Elmswell, Botesdale and Redgrave. Near Needham Market the Chalk yields Actimcamax quadratus, Inoceramus mytiloides and Ostrea acutirostris. There are Chalk pits at Coddenham, while to the north-east the Chalk appears in the Deben Valley below Debenham and at Earl Soham. Chalk above the zone of Actimcamax quadratus might have been expected along the borders of the Eocene covering from Sudbury, east- wards to Claydon and Bramford near Ipswich ; but at Sudbury no indi- cations of higher beds have been proved, the few fossils found there including Lima hoperi and teeth of the sharks Lamna and Oxyrhina. It is to be borne in mind that the thickness of Chalk proved at Combs near Stowmarket is but little less than that below Stutton, where the full local thickness occurs. Along the eastern borders of the county it may be that higher beds occur, but information derived solely from borings is necessarily meagre. The Chalk is the great storehouse for water, and wells and borings have been carried into it in all parts of the county, excepting into its lowest division of grey marl, which is impervious. Although so much of the Chalk is deeply buried beneath newer strata, which consist largely of impervious clays and effectually keep out the direct rainfall, yet an abundant supply of good water has been obtained at Ipswich, Wood- bridge and other places far from the main outcrop. Under such con- ditions a supply is not always freely obtained, and it may be necessary to penetrate the formation to depths ranging up to 250 feet before a fissure is met with ; while along the sea borders, as at Southwold, Leiston, Orford and Landguard Fort, brackish or saline waters have been encountered. In west Suffolk, where the Drift coverings are neither so thick nor so impervious as in central Suffolk, water is more readily obtained. Mr. Whitaker has called attention to an intermittent stream or ' nailbourne ' at Coddenham. After much dry weather, when the plane of saturation in the Chalk is low, the brook which flows over Boulder Clay in its higher course sinks into the permeable Chalk, but after long-continued rain there is a continuous flow of water.' The Chalk is burnt for lime at Sudbury, Bramford, near Bury St. Edmunds and other places; and it has been used with an admixture of river-mud for cement making at Waldringfield and Burgh Castle. In • 'Geology of the Neighbourhood of Stowmarket,' Geol. Survey (1881), p. 18, 7
