Page:VCH Norfolk 1.djvu/32

 A HISTORY OF NORFOLK The strata or formations known in Norfolk may be grouped as follows, the names in italics referring to those not exposed at the surface : — Period. Recent to Neolithic Pleistocene, Paleolithic and Glacial Pliocene Upper Cretaceous Lower Cretaceous Jurassic Formation. Alluvium, including Submerged Forest and Fen Beds. . . Blown Sand Shingle Beaches Brickearth. , Valley Gravel. Marine Gravel and Clay Plateau Gravel Boulder Clay. Glacial Sand and Gravel Glacial Loam and Marl Cromer Forest Bed. Norwich Crag Series London Clay Reading Beds Upper Chalk Middle Chalk Lower Chalk Red Chalk. Gault. . 'Carstonc »3
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Snettisham Beds. .Sandringham Beds Kimeridge Clay Corallian Oxford Clay Character of the strata. Mud, silt, clay, peat, marl and gravel Clean sand Chiefly flint pebbles Loam and marl Sub-angular flint gravel Shelly gravel and clay. Boulder gravel Chalky clay, with flints and erratics Shelly sand and gravel. Loam, with boulders and marl Gravel, laminated clay and peaty loam Shelly sand and gravel and laminated clay .... Grey clay and sandy clay. . Green sand and grey clay Soft chalk, with nodular flints and paramoudras Hard chalk, with nodular and tabular flints in upper part, and marly seams .... Hard grey and white limestone Red limestone Grey marly clay .... Brown ferruginous sandstone and grit Clay, with septarian nodules. Light-coloured sands and flaggy sandstone .... Dark shale and clay, with no- dules and bands of limestone Clay Clay, with septaria .... Approximate thickness in feet. 1 to 75 up to 6o up to 50 up to 15 up to 45 up to 30 I to 45 I to 130 I to 70 1 to 35 10 to 30 25 to 100 310 46 about 800 about 300 80 to 130 4 30 to 60 up to 40 o to 30 up to 100 thickness not proved The superficial extent of the various formations is depicted on the accompanying map. At present no borings in Norfolk have penetrated the Jurassic rocks. The deep boring at Norwich (see p. 7) touched the Gault, 2