Page:VCH Suffolk 1.djvu/43

 GEOLOGY EOCENE THANET BEDS The oldest Eocene strata in this country are the Thanet Beds, and their presence in the neighbourhood of Sudbury was made known in 1874 by Mr. Whitaker. Above the Chalk he observed at Ballingdon, a suburb on the Essex side, 14 feet of green clayey sand, which in all probability represents the Thanet Beds/ Traces of the same deposit, sometimes with green-coated flints, have also been observed by him At Cosford Bridge and Kersey Mill in the Brett valley, and at Somersham, Little Blakenham, Claydon, Barham, Bramford and Ipswich. Nucula and Cardium are the only fossils which have locally been found in the strata. READING BEDS Overlying the thin representative of the Thanet Beds, and other- wise persistent in Suffolk, is the variable group of strata known as the Reading Beds. They comprise alternations of mottled clay, brown and grey clay, grey and green sand, with occasional masses of concretionary sandstone of the nature of greywethers. Black flint pebbles occur here and there, but not in prominent layers ; and no fossils have been ob- served in the strata in Suffolk. The outcrop of the group can be traced by means of pits and borings from Sudbury to Kersey near Hadleigh and the neighbourhood of Ipswich, where the thickness is reckoned by Mr. Whitaker at 37 feet. The thickness however varies like the strata, even within short distances, being from 43 to a little over 60 feet in the neighbourhood of Felixstow, 36 feet at Trimley, 27 to 34 feet near Woodbridge, as much as 70 feet at Southwold, and nearly 80 at Leiston. In these localities our information is derived wholly from records fur- nished by well-sinkers. The main mass of the Reading Beds extends to Saxmundham and Lowestoft, but not so far inland as Beccles. The possible occurrence of an outlier of Reading Beds beneath Drift and Crag at Hoxne has been suggested by Mr. W. H. Dalton, and he records the occurrence of ' plastic blue loam ' near Halesworth which 'may belong to this series'; but the evidence in both cases is questionable.^ In a well made at Brettenham it is possible that Reading Beds occur beneath the Drift, but Mr. Whitaker, who has published the section, does not favour this view.^ The Reading Beds having a narrow outcrop and being much con- cealed by newer strata enter but little into the surface features of the county. The clays are worked for brick-making near Sudbury, Bram- ford and Ipswich, and the sandy beds are water-bearing. At Stoke near Ipswich Mr. Whitaker noticed a few feet of sandy ' Stuart. Joum. Geol. Soc. xxx. 401. » See ' Geology of the Country around Halesworth and Harleston,' Geol. Survey (1887), pp. 3. 37, 38- ^ ^art. Joum. Geol. Soc. lix.