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Upper Permian or St. Bee's Sandstone.
Red and green marls with gypsum
Yellow magnesian limestone with casts of fossils
Whitehaven sandstone (Coal-measures or Permian ?)
The sandstone of St. Bee's Head was used in the construc
tion of Furness Abbey.
Near Manchester the Permian beds consist of a series of red marls, clays, and sandstones, with bands of fossiliferous limestone, resting upon red sandstones (Collyhurst sandstone) and conglomerates: these again repose unconformably upon the Coal measures. The thickness is from 100 to 140 feet. In Durham, the Permian rocks are from 600 to 700 feet in thickness, consisting of the following beds :
Marl slate with fine specimens of fossil fish
Sandstone and gypseous marl, with plant remains
300 to 400
Traces of Permian rocks occur south of Ashby-de-laZouch, in Leicestershire; but according to Professor Ansted it is a doubtful fragmentary and unimportant deposit.' The beds occur in a gravelly and loose state, so that in one locality the deposit is known as the Poxon gravel.' 'It
is an interesting fact that the pebbles of the gravel and breccia forming the Permian deposits appear to have come from the west, no trace of Charnwood rocks having been discovered amongst them.'
In Nottinghamshire the following divisions have been made:
Red Marl and Sandstone.
Red and Purple Marls, with thin bands of Limestone.
The marls have in places been used for brick-making. Near Tadcaster, the lower Permian marls have yielded gypsum, formerly worked for Plaster of Paris.
Near Rotherham, beds of red sandstone (Rotherham red rock) are quarried for grindstones and for building purposes; and in the same neighbourhood is found a variety of Raddle or Reddle, much used in polishing lenses, &c. At Harthill, the red sandstone is worked for scythe-stones.
The Alberbury breccia, near Shrewsbury, is probably of Permian age. The conglomerates and breccias of Cumberland, South Staffordshire, Enville, the Lickey and Clent Hills, the Abberley and Malvern Hills are generally rough, coarse, and subangular; the stones and boulders being embedded in a red marly paste. In Professor Ramsay's opinion these are simply old boulder-clays, formed at a glacial period in Permian times.
At the Clent Hills, the Permian breccia is considered to be about 450 feet in thickness.
On the eastern face of the Malvern Hills is a band of brecciated rocks, termed by Professor Phillips the Haffield Conglomerate, which is about 200 feet in thickness.
Near Stafford the red sandstone has been worked for building purposes. In South Staffordshire the thickness of the Permian beds is estimated at from 1,000 to 3,000 feet; and in North Staffordshire from 500 to 700 feet.
In Cheshire the Permian beds attain a thickness of from 600 to 800 feet.
In the Vale of Clwyd traces of Permian beds have been indicated by Mr. Maw as resting on the Carboniferous Limestone, and being overlaid unconformably by Bunter beds.
In Anglesea the Permian beds rest unconformably upon the Coal-measures; they consist of red marls, sandstones, and conglomerates, and attain a thickness of nigh 400 feet.
1 Some observers have placed this rock in the Upper Coal-measures.
It has been suggested that certain breccias in Devonshire may be of Permian age.
(See p. 141.)
The term Trias has been adopted from the German geologists, being applied to the triple division that may be made in places on the Continent in this series of rocks. These three divisions are (in descending order) Keuper, Muschelkalk, and Bunter. The Muschelkalk, which is a grey shelly limestone, has not been identified in this country, and its absence has led many geologists to regard our Triassic series as incomplete, to identify in it only the upper and lower divisions of the German Trias, and to regard the Keuper as deposited unconformably upon the Bunter. The following shows this classification:
There seems to be no doubt that in some localities there are evidences of erosion or disturbance between the beds classed as Bunter and those classed as Keuper, but there does not appear to be any satisfactory evidence from which to conclude that such unconformability was produced at one time over the entire British area.
The absence of the Muschelkalk in the British area must not of itself be taken as any evidence whatever of an unconformability, considering the very variable nature of the Triassic strata, and of the conditions under which the beds were deposited in different areas.
The use of the terms Bunter and Keuper is convenient,
although the beds in our country so designated cannot be correlated in time with exactness with the rocks distinguished by those names on the Continent. In the same way, where the Oxford and Kimeridge clays come together without the intervention of the Coral Rag series, and without unconformability, we cannot perhaps identify the exact equivalent of the Coral Rag, and cannot do better than use the purely lithological terms.
NEW RED SANDSTONE.
The Bunter (variegated) Sandstone of Germany was first identified in England in 1826 by Sedgwick.
The general divisions of the Bunter beds are thus given by Professor Hull :
Upper Mottled Sandstone.-Soft, bright, red, and variegated sandstone.
Pebble Beds or Conglomerate.-Harder reddish brown sandstones, with quartzose pebbles, passing into conglomerate; with a base of calcareous breccia.
Lower Mottled Sandstone.-Soft, bright, red, and variegated sandstone, showing much false bedding.
The Lower Mottled Sandstone attains a thickness of about 650 feet at Bridgenorth; in Cheshire it is 400 feet; at St. Helen's Junction it is about 250 feet; and in South Staffordshire 200 feet.
The Pebble beds attain a thickness of from 60 or 80 feet to 600 feet. They are composed chiefly of quartz, the pebbles of which (according to Mr. Aveline) are found either loosely scattered amongst unconsolidated sand, or cemented into a hard conglomerate. So gradually do they pass into
the sandstones below that there is no very definite line of separation.
The Upper Mottled Sandstone attains a thickness varying from 200 feet to as much as 700 feet at Delamere Forest.
The total thickness of the Bunter beds is estimated at 1,000 to 2,000 feet.
The Hemlock or Himlock Stone, near Nottingham, consists of the Lower Mottled Sandstone capped by the Pebble beds. In this locality the sandstone is about 80 feet thick, but further towards Nottingham it has a thickness of 100 feet.
The Vale of Clwyd is formed in the Bunter sandstone, belonging in all probability, according to Professor Hull, to the Lower Mottled Sandstone; but sections are rarely seen owing to the covering of drift. In the Bridgenorth district these beds form the fine ridges of Apley Terrace, Pendlestone Rock, Abbot's Castle Hill, and Kinver Edge.
The beds may also be studied near Market Drayton, Cannock Chase, and Sherwood Forest.1
The greater part of Nottingham is built on a coarse white sandstone, containing scattered pebbles of quartzite, &c., belonging to the conglomerate division, according to Professor Hull. The old castle stood on a cliff of the same rock. Artificial caverns have been excavated in it.
In the Liverpool district the beds are represented by reddish-brown pebbly sandstone, largely quarried for building purposes.
The Upper Red and Mottled Sandstone, both in structure and composition, appears to be the most uniform division of the Bunter. In the neighbourhood of Birkenhead, Liverpool, and Ormskirk, the lower portion of this sub-division is red, the upper yellow, and sometimes
It is owing to its poor sandy and gravelly soil that the Forest of Sherwood existed so long, the greater part being still retained as woodland or common. (Aveline.)