Page:VCH Suffolk 1.djvu/37

 GEOLOGY Period Formation Character of the Strata Approximate thick- ness in feet Recent to Neolithic Alluvium, including sub- merged Forest and Fen Beds Blown Sand Shingle Beaches. . . Mud, silt, clay, peat and gravel Clean sand Chiefly flint pebbles. . 10 to 50 10 to 15 up to 50 Pleistocene, Palaeolithic and Glacial Valley Gravel and Brick- earth Boulder Clay .... Glacial Sand and Gravel. Glacial Loam .... Sub-angular flint gravel and loam Chalky clay, with flints and erratics .... Shelly sand and gravel Loam 10 to 25 up to 170 10 to 100 10 to 25 Pliocene Cromer Forest Bed. . Norwich Crag Series with Chillesford Clay Red Crag Series Coralline Crag .... Gravel, laminated clay and peaty loam with rootlets Shelly sand and gravel and laminated clay. Red and brown shelly sand Calcareous shelly sand and sandy limestone. . . 10 to 25 20 to 150 10 to 40 40 to 60 Eocene London Clay .... Reading Beds .... Thanet Beds .... Brown and blue clay with septaria and sandy clay Mottled clay, sand and sandstone Green clayey sand. up to 130 20 to 70 10 to 15 Upper Cretaceous Upper Chalk .... Middle Chalk .... Lower Chalk .... Gault Soft chalk with nodular flints Harder chalk with few nodular and tabular flints Grey and white blocky chalk with curved joint- ing and grey marl. Grey marly clay. . . 500 200 to 220 160 to 170 50 to 90 Lower Cretaceous Lower Greemand. Ferruginous and calcareous sandstone 30 to 35 Jurassic Kimeridge Clay .... Dark shale with bands and nodules of lime- stone 100 Palasozoic Silurian ? (or older) Slaty rock unknown PALAEOZOIC Rocks of ancient date, the age of which cannot at present be deter- mined, have been proved at Stutton in the low ground south of Crepping Hall, on the borders of the Stour. There at a depth of 994 feet beneath Gault, Chalk and other over- 3