GEOLOGY TABLE OF STRATA Formation Approximate Period Character of material thickness in feet Recent Alluvium Mud, silt, gravel, etc., at low levels in present valleys rarely exceeding 20 High-level Valley-gravel Gravel, sand, sandy loam, etc., of rarely and Brick-earth ancient river terraces exceeding 20 Pleistocene Clay with Flints Angular flints and clay overlyingl Chalk irregular, in 'pipes,' up to ( 20 or more Plateau Gravel Gravel, chiefly of flint, but with some pebbles of quartz, quartzite, etc. rarely exceeding 1 5 Older Pliocene (?) Lenham Beds (?) Ferruginous sand and sandstone in fissures at the top of the Chalk f ("Upper Bagshot Sand Yellowish sands up to 150 Bracklesham Beds o < Clay laminated with sand 40 to 60 > 1 Lower Bagshot Sand pa * Light-coloured micaceous sands with a few pebbles 100 to 150 T _ ~,. _ - London Clay
- fi
Stiff blue or brownish clay with layers of nodules 400 to 480 1 3 xLocene | Oldhaven or Black- s' heath Beds Rolled flint-pebbles with a little sand up to 60
o .g Woolwich and Read- (3 Clay, loam and sand, usually of bright 70 fn Rn JB
- j
O lj ing Beds varied colours <W LJ OJ M
1 Thanet Beds Light-coloured sand with green-coated up to So o J flints at base r J o. Upper and Middle Chalk Soft chalk, with flints 500 or more X W Upper Cretaceous Lower Chalk with Chalk Marl a r '1 Upper Greensand O "i Chalk, without flints Calcareous marl Glauconitic sand and marl, and cal- careous sandstone with chert 200 or more 30 to 100 30 to 1 50 I [Gault Stiff clay and sandy clay 100 to 150 | ("Folkestone Beds Coarse sand and ferruginous concretions 130 to 1 60 j Sand gate Beds Sand, sandstone and fuller's earth up to 50 <jf HytheBeds V Sand, with some sandstone, ironstone and chert 180 to 250 1 'Atherfield Clay Clay, sometimes sandy up to 60 ( Clay and shale, mostly dark-coloured, T nwpr Weald Clay .[ with thin bands of shelly lime- 1000 I >< ' WCl Irptapprtiic ( stone and ironstone nodules V^l v_ Lttk.CUU.3 d " Upper Tunbridge Wells Sand Sand and soft sandstone 150 s ' ? Grinstead Clay Clay, usually red or greenish 3 l> '/. !> I Lower Tunbridge Wells Sand Sand and soft sandstone 60 s Wadhurst Clay Clay and shale with ironstone bands 150 Ashdown Sand Sand and soft sandstone 300 or more r 11 Jurassic Great Oolite Series Oolitic limestone, calcareous sand- stone and thin bands of clay see p. 19 I 1
Triassic (?) (or older) New Red Sandstone (?) Red, white and mottled sandstone, with marls see p. 21
