On the “Caradoc Sandstone” of Shropshire

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Abstract
Summary: The conclusions to be drawn from the foregoing data may be thus shortly stated. The rocks east of the Longmynd hitherto known as Caradoc sandstone are now divided into two groups. The lowest and greatest portion is equivalent to the middle and upper portions of the Llandeilo and Bala rocks, and were accumulated in the following order:— 1. Fine shales, with small Trilobites ( Olenus, Asaphus, Agnostus ) and shells, deposited in deep water (most probably the equivalents of the Black Shales, Malvern). Elevation of Land, or Shallowing of Sea. 2. Coarse calcareous grits and conglomerate; a littoral or shallow water deposit. 3,4. Sandstones, with occasional pebbles, laminated in the upper parts, and in some localities northwards with many beds of shale. finer deposit than the last, and indicating a greater depth of water. Fossils exactly those of Bala. 5. Thin-bedded arenaceous shales, with fewer fossils, but of the same species; Trinucleus concentricus very abundant. A still greater depth of water is here indicated. (The higher part of the Llandeilo or Bala series.) Evidence of upheaval and partial dislocation. 6. A coarse deposit (unconformable on Nos. 1 to 5) in the immediate neighbourhood of the Longmynds, and derived from them (in part deep water around steep land, Forbes ). A great change in the organic remains. The characteristic Llandeilo and Bala fossils have given place to a mixed series, including several species found in the Upper Llandeilo flags, but with many others more characteristic of the Wenlock limestone. 7. Finer sandstones, with much shale and great abundance of Pentameri , and other Brachiopoda. Land gradually sinking ( Ramsay , Geol. Journ. vol. ix. p. 175). Fossils chiefly Upper Silurian. 8, 9. Grey and greenish shales, very fine sediment: deep water. Trilobites, Graptolites, and Cephalopods abundant. Fossils all Upper Silurian.

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