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GEOLOGY Period Formation Character of the strata Approximate thickness in feet Recent Alluvium Gravel, sand, loam, clay, and peat, along present streams . up to 2O ? Pleistocene Brickearth, Valley Gravel Glacial Drift . Loam, sand, and gravel of old river-courses up to 2O ? Sand, gravel, stony clay ; boulders of distant rocks . up to i oo ? Jurassic Great Oolite Series . Inferior Oolite Series. f Upper . . . Lias ] Middle. . . V Lower . Oolitic limestones and clays, with sandstones . . . . 80 to 100 Oolitic limestones, with sands and calcareous sandstone . 80 to 1 50 Clay and shale, with limestones and calcareous sandstones . 120 Hard ferruginous limestone, sands and shales .... 280 Clays and shales, with clayey limestones in lower part . up to 960 Rhaetic Marl Keuper Triassic Bunter - Sandstone Upper . Middle. ? Lower White and grey limestones, dark shales, and yellow sandstone Red marl, mottled green ; green and buff (20 to 30 feet) at summit .... Red and brown sandstones and marls Fine red sandstone, without pebbles Pebbly red sandstone, with pebble-beds Yellow sandstone, without pebbles ' Permian ' of Salopian type . Car- boniferous Coal Measures- Newer (barren) measures . Older (produc- tive) measures Red sandstones and marls, with limestone-conglomerate . Sandstones and shales, with brick-clays and Spirorbis limestones Sandstones and shales, with seams of coal, ironstone, and 30 to 40 600 to 700 150 to 200 200 250 to 350 2,000 I,OOO fireclay , Cambrian Upper : Stockingford Shales Lower : Hartshill Quartzite Grey, black, and purple shales 2,000 Grey quartzites and sandstones, with purple and grey shales and a thin limestone. . . 600 Archaean Uriconian and Upper Long- myndian. Caldecote series . Volcanic breccias, tuffs, and ~ ? several grits ) hundred /Diorites(Camptonites) ; Intrusive post -Cambrian but Igneous ! pre-Carboniferous Rocks Porphyritic Basalt ; of V. pre-Cambrian age . Of -various ages [Crystalline igneous rocks