Wenlock Series

The Wenlock Group (Wenlockian), in geology, is the middle series of strata in the Silurian (Upper Silurian) of Great Britain. This group in the typical area in the Welsh border counties contains the following formations: Much Wenlock Limestone Formation, 90–300 ft.; Wenlock Shale, up to 1900 ft.; Woolhope or Barr Limestone and shale, 150 ft.

The Woolhope Beds consist mainly of shales which are generally calcareous and pass frequently into irregular nodular and lenticular limestone. In the Malvern Hills there is much shale at the base, and in places the limestone may be absent. These beds are best developed in Herefordshire; they appear also at May Hill in Gloucestershire and in Radnorshire. Common fossils are Phacops caudatus, Encrinurus tuberculatus, Orthis calligramma, Atrypa reticularis, and Orthoceras annulatum.

The Wenlock Shales are pale or dark-grey shales which extend through Coalbrookdale in Shropshire, through Radnorshire into Carmarthenshire. They appear again southward in the Silurian patches in Gloucestershire, Herefordshire and Monmouthshire. They thicken from the south northward. The fossils are on the whole closely similar to those in the limestones above with the natural difference that corals are comparatively rare in the shales, while graptolites are abundant. Six graptolite zones have been recognized by G. L. Elles in this formation.

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