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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