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At Malvern, the Wenlock Shale, consisting of dark blue or grey sandy shale with thin bands of limestone-nodules, is estimated by Professor Phillips to have a thickness of 640 feet.
The Wenlock Shale contains several species of Orthis, Leptæna, and Rhynchonella, also Euomphalus, Bellerophon, Theca, and Orthoceras. Encrinurus, Calymene, Sphære.cochus, and Phacops. Crinoids also are not uncommon.
WENLOCK LIMESTONE. (Murchison.)
HAY HEAD or BARR LIMESTONE. (Walsall.) The Wenlock Limestone consists of thick beds of concretionary or nodular limestone of a light grey colour, containing numerous fossils and separated by beds of shale. It rests conformably upon the Wenlock Shale.
In parts of Wenlock Edge the rock is more crystalline ; and where varied colours prevail, the matrix being charged with Encrinites and corals, it forms a pretty marble, though the slabs are of no great dimensions. (Murchison.)
Some of the beds consisting of impure earthy limestone and shale, contain large concretionary masses of good limestone, called “wool-packs' or “ballstones:' some of them near Wenlock have, according to Murchison, a diameter of 80 feet, and they are quarried out, leaving large cavities. The same geologist observes that, though very thick near Wenlock, the limestone thins out so rapidly in its range to the south-west, that even in the interior of the Ludlow promontory it is represented by thin courses made up of small concretions only, and near Aymestry it is merely represented by a few concretions, varying in size from 2 inches to 2 feet, but still full of beautiful and characteristic corals. It thins out entirely in Radnorshire, and is very feebly represented in Brecon, Caermarthen, and Pembroke; for, according to Murchison,
its place is only marked in the cliffs of Marloes Bay, west of Milford Haven, by some fossils and a small quantity of impure limestone in grey and sandy shale.
The Wenlock Limestone is well-developed at Malvern (290 feet), Woolhope, May Hill, and Usk. Among the most noted localities, however, are the Castle Hill and Wren's Nest at Dudley, where the limestone has been largely quarried ; also Hurst Hill near Sedgley.
The northern end of Wenlock Edge, Benthall Edge, and Gliddon Hill are mentioned by Murchison as the best localities for fossils.
The fossils comprise Corals, Encrinites, Trilobites, Mollusca, and Annelides, including species of Halysites, Favosites, Heliolites, Omphyma, Cyathophyllum ; Periechocrinus moniliformis; Illanus Barriensis (Barr trilobite), Encrinurus, Phacops Downingiæ, P.caudatus, Calymene Blumenbachii (the Dudley Locust '), Pterygotus ; Orthoceras annulatum, Bellerophon, Conularia, Orthonota, Avicula, Strophomena, Pentamerus, Spirifer, Orthis, Atrypa, Rhynchonella borealis; and species of Cornulites and Tentaculites.
The limestone is largely quarried for smelting-purposes and lime-burning at May Hill, Ledbury, Woolhope, and Abberley. The Ledbury Marble is an oolitic limestone.
LOWER LUDLOW BEDS. (Murchison.)
The term is derived from the town of Ludlow in Shropshire, and the formation consists of grey sandy shales, locally called mudstones ; some of the upper beds are calcareous.
The Ludlow formation is a natural continuation of the Wenlock beds, and the inferior strata contain calcareous nodules, which differ from those of the Wenlock deposit only in being usually of a blacker colour, and which have often been formed round an Orthoceras, a Trilobite, or other fossil as a nucleus. (Murchison.) The thickness of the formation is about 700 feet at Malvern.
Amongst the fossils are numerous Starfishes, Palasterina, Palæaster, Palæocoma, Protaster; many Crustacea, Pterygotus, Hemiaspis (4 species), Eurypterus punctatus, E. Brodiei, Ceratiocaris Ludensis, Trilobites, &c.; Graptolites; Cardiola interrupta, Murchisonia Lloydii, Orthoceras Ludense, Phragmoceras, Lituites, Lingula lata.
In ascending, the strata (according to Murchison) become somewhat more sandy, constituting thick fagstones called ‘pendle' by the workmen. They have attracted much attention at a spot near Leintwardine, and have yielded many remains of Crustacea and Starfishes. These beds, says the same authority, form the support of the Aymestry limestone, from which they are usually separated by soft soapy beds, in parts an imperfect fuller's earth. It is the decomposition of this unctuous fuller's earth (provincially Walker's earth) beneath heavy masses of the limestone which rest upon it, which has occasioned numerous landslips both near Ludlow and in neighbouring parts of Herefordshire. The Lower Ludlow Shale as described by Murchison occupies the escarpments and contiguous valleys of the Ludlow rocks which range from Shropshire by Presteign to Radnor Forest, and also large undulating tracts of the western parts of Shropshire or contiguous parts of Montgomeryshire. In the Usk, Tort worth, Woolhope, and Malvern districts it is well known.
BANNIS DALE SLATES.
IRELETH SLATE GROUP in part. (Sedgwick.) This group, as developed in the Lake District, is placed on the horizon of the Lower Ludlow and Wenlock Shale.
The Bannisdale Slates are described by Mr. Aveline as consisting of sandy mudstones divided by thin bands of hard sandstone and occasional beds of grit. The sandy mudstones are much jointed and roughly cleaved, never making good slates, but often large rough slabs, quarried for paving or building stones. The total thickness of the formation is about 5,200 feet.
Fossils are scarce : they include Rhynchonella navicula and Phacops Downingice.
The lowest beds are seen near Kirkby Lonsdale.
AYMESTRY LIMESTONE. (Murchison.)
The Aymestry or Ludlow Limestone occurs in beds of a concretionary character, though this feature is not so conspicuous in them as in the Wenlock Limestone. It is of a bluish-grey and mottled colour, containing numerous layers of shells and corals, and associated with it are beds of shale. It occurs in strata from one to five feet in thickness, but these are very impersistent. Salter indeed regarded it as only a calcareous condition of the Lower Ludlow formation. It may be traced in Herefordshire, Shropshire, and Staffordshire, where it is often extensively worked. South-west of Aymestry it thins out, but it is represented at Usk, May Hill, Abberley, Malvern, &c. Its thickness may reach from 30 to 40 feet.
The fossils include Protaster, Palæaster, Phacops, Calymeme, Acidaspie, Ceratiocaris, Pte got 8, Slimomia; also many species of Mollusca, Pentamerus Knightii, Rhynchonella, Lingula, Strophomenu, Atrypa, Bellerophon, &c.
UPPER LUDLOW BEDS. (Murchison.)
These beds consist of flaggy arenaceous shale, with beds of thin shelly limestone. Some of the lower beds are termed mudstones. Their thickness near Ledbury is 140 feet.
The beds yield among Crustacea, Eurypterus, Pterygotus, Hemispie, Slimonia, Phacops, Homalomotus Knight; also Orthoceras bullatum, Pteropods, Gasteropods, Lamellibranchs, and Brachiopods.
The base of the rock is sometimes marked by calcareous shelly courses, containing Terebratula (Rhynchonella) navicula, and Leptæna lævigata.
The beds are well shown at Ludlow, Ledbury, Malvern, Abberley, near Usk, &c. They are extensively quarried for building purposes.
The uppermost Ludlow rocks consist of finely laminated greenish-grey sandstones, overlaid by the Ludlow Bone-beda thin layer, of from one inch to a foot in thickness, made up of a mass of bony fragments of fish-defences, coprolites, spines of Onchus tenuistriatus, and fragments of Pteraspis--some of a mahogany hue, others black-also remains of Crustacea (Ceratiocuris ? ).
KIRKBY MOOR FLAGS.
KENDAL Group. (Sedgwick.)
This formation includes red calcareous flagstones and grits, sometimes in thick beds, and of coarse texture; also bands of coarse slate and tilestone.
It is placed on the horizon of the Upper Ludlow series; and it passes downwards into the Bannisdale Slate group. It extends from Benson Knot, south of Kendal, through Kirkby Moor to the Lune.
The upper part contains casts and impressions of Terebratula, Orthis, Orbicula, Pterinea, Avicula, Orthonota, Turritella, Orthoceras.
The most common and characteristic species are stated by Mr. Aveline to be Holopella gregaria, H. conica, and Chonetes lata.
The beds occur at Hay Fell, Kendal, &c.