Page:VCH Northamptonshire 1.djvu/32

 TABLE OF FORMATIONS Era or Group Period, or System Formation Character of the strata in Northamptonshire Approximate maximum thickness in feet Recent Alluvium .... Dark carbonaceous mud or loam. IS Quaternary or Post- Tertiary Recent and (or) Pleistocene Fen-land .... Valley Gravels. . Gravels, sands, clays and peat. Alluvial gravels and sands. . . ? 35 Pleistocene Upper Boulder Clay. Mid-glacial Gravels. Lower Boulder Clay and Sands Clay, with much chalk and many erratics Coarse gravel to fine sand. . . Gravels, sands, loams and clays ; few erratics 100 35 170 Cainozoic, or Tertiary Pliocene, Oligocene, Eocene (absent) Upper Cretaceous, Lower Cretaceous and Upper Oolitic (absent) Middle Oolitic Corallian Beds. . . Oxford Clay. . . Kellaways Rock & Clay Dull slate-coloured clay and shale. Grey shale and blue clay. . ? 10 f Lower Oolitic Great Oolite Series Cornbrash .... Forest Marble Series. Great Oolite Clay Great Oolite Limestone Upper Estuarine Beds White, ruddy, or blue limestone. Variegated clays and fissile limestones Blue and purple clay, with ironstone nodules White, or yellowish limestone. . Variegated clays, thin limestones, oyster beds, etc 15 8 12 25 30 Mesozoic, or Secondary Inferior Oolite Series Lincolnshire Oolite. Lower Estuarine Beds (part of North. Sand) Northampton Sand. Oolitic and shelly limestones & slates White and ruddy sands and clays, carbonaceous Ironstones, sandstones, calcareous beds 85 15 60 Liassic Upper Lias .... Middle Lias. . . Lower Lias. . . Blue clay, with cement stones and stone beds Grey micaceous clays, marls, cal- careous and sandy beds. . . Blue clays with cement stones and limestone bands 180 98 520 Triassic Rhaetic Beds. . . Keuper Bunter Black shale and white limestone, etc. Variously coloured sandstones and marls, etc (absent) 36 107 Permian (absent) Palaeozoic, or Primary Carboniferous Coal Measures. . . Millstone Grit. . . Carboniferous Lime- stone Series (absent ?) (absent ?) Dolomite, limestone, sandstone, marl, etc 190 Old Red Sandstone and Devonian Old Red Sandstone. Red sandstone, grits and marls to 105 Silurian and Cambrian (not yet found) Azoic Archaean Contemporaneous volcanic rocks. to 74