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 



