In the Chatwall district, Shropshire, western England, the Ordovician strata comprise the Harnage shales and the Chatwall group, which includes the lower and upper Chatwall sandstones and the overlying Alternata limestone. Recent mapping has now made possible a detailed section and faunal succession, and several changes in the nomenclature are suggested. The Harnage shales should be used in a broad sense, for they probably also include the Glenburrell beds. The overlying beds are the Chatwall or Glyptocrinus flags, while the term Chatwall sandstone should be restricted to the beds of the lower Longvillian stage, and the Alternata limestone applied to the upper Longvillian.

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