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 .
- vAshdown Sand .
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
