Page:A Treatise on Geology, volume 1.djvu/71

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CHAP. IV
55
SERIES OF STRATIFIED ROCKS.
Oolitic System.
Names of formations. Thickness
in yards.
Subdivisions or groups. Nature of the deposits.
Wealden. 300 \left\{ \begin{matrix}\ \\ \ \\ \ \end{matrix} \right. Weald clay. Clays and calcareous layers.
Hastings sands. Variously coloured sands and clays.
Purbeck beds. Clays and limestones.
Upper oolite. 130 \left\{ \begin{matrix}\ \\ \ \end{matrix} \right. Portland oolite. Limestone, often cherty, with sand.
Kimmeridge clay. Blue clay, with septaria.
Middle oolite. 150 \left\{ \begin{matrix}\ \\ \ \\ \ \\ \ \\ \ \\ \ \end{matrix} \right. Upper calcareous grit. Sandstone (calcareous).
Coralline oolite. Oolitic limestone.
Lower calcareous grit. Sandstone (calcareous).
Oxford clay. Blue clay, with septaria.
Kelloway rock. Sandstone (calcareous).
Lower oolite.[1] 130 \left\{ \begin{matrix}\ \\ \ \\ \ \\ \ \\ \ \\ \ \\ \ \end{matrix} \right. Cornbrash. Coarse limestone.
Forest marble. Coarse limestone, sands, and clays.
Great oolite. Limestone, oolitic, compact or sandy.
Fullers' earth. Limestones, clays, &c.
Inferior oolite. Limestone, oolitic, ferruginous.
Sand. Calcareous or ferruginous sand and sandstone.
Lias. 350 \left\{ \begin{matrix}\ \\ \ \\ \ \\ \ \\ \ \end{matrix} \right. Upper lias shale. Blue laminated clay.
Marlstone. Sandy, calcareous, and irony beds.
Middle lias shale. Blue laminated clay.
Lias limestone. Blue and white compact limestones.
Lower lias marls. Clays of different colours.
Saliferous or New Red Sandstone System.
New red sandstone. 300 \left\{ \begin{matrix}\ \\ \ \\ \ \\ \ \\ \ \\ \ \\ \ \end{matrix} \right. Variegated clays. Red, greenish, &c. clays, with gypsum.
Keuper. Sandstones, usually light-coloured, with plants, and vertebrata.
Red clays. Red clays, with a few pale bands, gypsum, salt, &c.
Sandstone. Red and white sandstone, with bands of clay.
Conglomerate. Sand and sandstone, with pebbles of quartz, porphyry, &c.
  1. As seen near Bath. In other parts of England it offers important differences, as will appear hereafter.