Page:VCH Suffolk 1.djvu/45

 GEOLOGY Where exposed at the surface the London Clay would under ordi- nary circumstances yield a stiff clayey soil, but in Suffolk it is mainly exposed along the borders of valleys and the soil is lightened and en- riched by down washes from higher sandy and shelly strata. The soil has therefore been described as a ' rich loam,' and as such it is met with here and there from Hadleigh eastwards to the borders of the Stour, Orwell and Deben. It is impossible now to say how far the Eocene strata formerly ex- tended over Suffolk. In some areas deep ' pipes ' in the Chalk have preserved portions of the strata at a distance from the main mass, but apart from the doubtful evidence furnished by well sections no such relics have at present been proved to occur in Suffolk. It may be that there was overlap of the successive members of the Eocene series, and that Bagshot Beds formerly extended into the county, yielding materials for some of the Pliocene and Glacial sands and pebble beds. Indeed, S. V. Wood, jun., suggested that the middle Glacial sands might largely have been made up of Bagshot Beds.' The occur- rence moreover of Oligocene fossils in the basement beds of the Crag in Norfolk is also a significant fact. The Chalk surface has been furrowed in places by ' pipes ' and traces of clay-with-flints were noticed by Mr. F. J. Bennett in such pipes beneath Boulder Clay near Saxham," while irregular channels have occasionally been formed in Pleistocene times and filled with Glacial Drift. Some disturbances have been proved in the Chalk south of Ipswich and at Woodbridge,^ while a few small faults have been noticed in the London Clay at Felixstow and Bawdsey. PLIOCENE The Crag Series consists of sands, pebbly gravels and laminated clays, but the characteristic and prominent beds are shelly sands which have for a long period been dug as manure for fertilizing the land and as material for garden walks.* CORALLINE CRAG The lowest division, known as the Coralline Crag, owes its name to the fact that much of it is composed of bryozoa. In some places it appears in the form of loose shelly sands ; elsewhere it is composed of comminuted shells and bryozoa, locally hardened into stone, the joints • ' Remarks in Explanation of Map of the Upper Tertiaries of the Counties of Norfolk, Sufiblk, etc' (1866), p. 13. ' * Geology of Bury St. Edmunds,' p. 12. ' Whitaker, ' Geology of Ipswich,' p. loo ; and ^uart. Joum. Gnl. See. lix. Soc. ; Prestwich, Quart. Journ. Geol. Soc. xxvii. 115, 325, 452 ; F. W. Harmer, ibid. liv. 308, lyi. 705 ; Whiuker, 'Geology of the country around Ipswich,' p. 32 ; C. Reid, 'The Pliocene Deposits of Britain' (1890), Geol. Survey ; and E. T. Newton, 'The Vertebrata of the Pliocene Deposits of Britain ' (1891), Geol. Survey. II
 * For full particulars of the Pliocene strata, see S. V. Wood, 'The Crag Mollusca,' PaUmtograph.