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 GEOLOGY II. TABLE OF STRATA IN KENT : a. Strata Exposed at the Surface Period Recent Formation Alluvium, Beach- shingle, Blown Sand, etc. Character of Material Mud, silt, gravel, etc., at low levels in river-valleys, and marine and estuarine deposits above average high tides Approximate thickness in feet up to 40 Pleistocene Older Pliocene Old River Drift. . ' Superficial ' Deposits on the Chalk Gravel, sand, loam (brick-earth), etc., of ancient river-terraces Clay - with - flints, brick-earth and pebbly loam up to 45 up to 30 ft. or more in fis- sures, but thin elsewhere Lenham Beds Yellow sand and sandy iron- stone mainly in 'pipes' or fissures of the Chalk Eocene Upper Cretaceous Lower Bagshot Beds London Clay. . Oldhaven or Black- heath Beds Woolwich and Reading Beds Thanet Beds. . Sand and loam with clay part- ings (in Isle of Sheppey only) Stiff blue or brownish clay with nodules of * cement stone ' and pyrites. . . Light-coloured sands and beds of smooth flint pebbles. Loam, clay, and light-coloured sand, with some flint-pebble beds Fine pale sand, often rather loamy, with green-coated flints at base. ., Upper Chalk. . Middle Chalk. . Lower Chalk with Chalk Marl Upper Greensand Gault. . I Soft white chalk, with flints White chalk, with some flints Grey chalk without flints, anc calcareous marl. . . Grey marly sandstone and glau- conitic marl .... Stiff clay, in part marly. . up to about 20 400 to 480 20 to 50 up to 50 up to 65 450 26s o to I o ? [20 to 200 Lower Cretaceous Folkestone Beds Sandgate Beds Hythe Beds. Atherfield Clay Weald Clay . /Tunbridgc Wells cq I Sand S>-jWadhurst Clay. Coarse sand with stone band: Clay, silt and fine sand. Loamy sand and soft sandstone with hard sandy limestone and some chert. . Stiff brown or bluish clay Clay, usually dark blue, but sometimes mottled red and yellow, with thin shelly limestone bands. . . . Sand and soft sandstone. . . Dark clay and shale, with iron- stone Sand and soft sandstone. . . 90 to IK 5 to 80 60 to 180 20 or more up to 700 150 to 180 160 to 180 300 or more
 * vAshdown Sand.