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The Dogger itself has been much worked for iron-ore. The magnetic iron-ore of Rosedale is worked in this series; and Prof. Phillips considers that this ore, and those of Thirsk and Kirkham, are the equivalents of the Northamptonshire iron-ores.
The Dogger is placed on the horizon of the Inferior Oolite, so that the sands below are homotaxeous with the Midford Sands.
Lower Shale and Sandstone (Yorkshire).
LOWER ESTUARINE BEDS.
This series, which rests upon the Dogger, comprises alternating beds of sands, sandstone, and shale, with oolitic ironstone, and much carbonaceous matter, and attains a thickness of 280 feet. The beds, as a rule, contain no marine shells, but many plant-remains.
The Great Sandrock,' 50 to 100 feet, occurs at or near the base of the series: it is largely used for building-stone.' Mr. Hudleston observes that the group thins out towards the south and west of the Oolitic area; it, however, constitutes a large portion of the Staintondale Cliffs, where, in certain layers of nodular ironstone, many species of ferns are nicely preserved. The beds appear in the cliffs from Robin Hood's Bay to Huntcliff.
Millepore Bed (Yorkshire).
This bed, so named from the occurrence of Cricopora (Spiropora) straminea, occurs as a limestone in Gristhorpe Whitby) has received its name from the lines of nodules, so characteristic of it, or from the peculiar appearance which the rock assumes owing to the rounding off of the huge oblong blocks, produced by the arrangement of the jointing. (W. H. Hudleston.)
1 Whitby Abbey was constructed of this stone.
Bay; nearer Scarborough it is obliquely laminated and arenaceous, and it is still more sandy at Cloughton Wyke. Dr. Wright correlates the Whitwell limestones of the Howardian Hills with this bed, and the slaty limestones of Brandsby appear to be on the same horizon. It is from 12 to 30 feet in thickness.
It is continued in the Cave Oolite and Lincolnshire Limestone, and, as Mr. Hudleston considers, may therefore, with the Whitwell and Crambeck Limestone, be the chief representative of the Inferior Oolite in Yorkshire.
The bed yields Lima duplicata, Gervillia Hartmanni, Pinna cuneata, Ceromya Bajociana, &c. Most of the fossils have been obtained from Sycarham, near Cloughton Wyke.
Middle Shale and Sandstone (Yorkshire).
MIDDLE ESTUARINE BEDS.
This group of Shales and Sandstones (Block Sand rock), from about 40 to 100 feet in thickness, contains many plantremains, ironstone-nodules, seams of coal, and sometimes jet.
The thickest seam of Moorland coal varies from a few inches to 18 inches in thickness. Mr. Hudleston observes that it is of little economic value, but it is remarkable for its persistency over a very large area, extending from the coast inland as far as Castleton and Coxwold.
At Gristhorpe the plant-bed has yielded many cycads, and ferns such as Sphenopteris, Pecopteris, Neuropteris, &c., also Equisetites columnaris.
This deposit comprises a series of blue and grey limestones (= 'Grey limestone' of Dr. Wright), with occasional shales and mudstones, 20 to 60 feet in thickness.
The beds yield Belemnites elongatus, Avicula Braamburiensis, Gervillia acuta, Perna rugosa, Pecten lens, Pinna cuneata, Trigonia costata, Gresslya peregrina, &c. Many species have been obtained at Hundale.
According to Mr. Hudleston the beds are feebly developed at Gristhorpe Bay (8 feet), but make a better show at White Nab and in Scarborough Bay.1
Stonecliff Wood Series.-This series, named by Mr. Hudleston, consists of sands containing towards the base and upper part intercalated beds and lenticular masses (potlids) of arenaceous and siliceous limestone; it is altogether about 30 feet in thickness.
The beds form a sort of escarpment facing the Derwent Valley. Some of the stone beds are used for building purposes. The fossil remains, including Avicula Braamburiensis, Gervillia acuta, Perna rugosa, and Mytilus sublævis, seem to link the beds with the Scarborough Limestone.
. At Collyweston, near Stamford, certain fissile calcareous. sandstones, or sandy limestones, which, after exposure, split up horizontally and form flagstones, have been quarried for roofing-purposes during the past four hundred years, and are termed the Collyweston Slates.
These beds overlie the Northampton Sands. The surfaces of the slates, as mentioned by Mr. Judd, exhibit the proximity of the shore, in ripple-markings, worm-tracks, and burrows, as well as by numerous plant-remains.
The fossils of the Collyweston Slates include Pecten pumilus, Avicula Braamburiensis, Pinna cuneata, Gervillia
1 Mr. Sharp considers these beds to be in all probability nearly synchronous with the Lincolnshire Limestone (Inferior Oolite). Phillips placed them with the Great Oolite.
acuta, Trigonia costata, Pholadomya fidicula, Ceromya Bajociana, Goniomya literata, Perna rugosa, &c.
These slates, according to Prof. Morris, may partly represent the beds which overlie the Dogger in Yorkshire (the Lower Shale and Sandstone).
They are quarried at Collyweston, Wittering, Easton, Deene, and Kirby.
The work of quarrying is carried on only in winter, for, if dried by the summer sun and wind, the rock hardens and will not split. The holes are blocked up in spring, and the quarrymen then employ their time in the preparation of the 'slate.' The splitting is caused by the presence of organic remains. (Phillips.)
Overlying the Collyweston Slates of Stamford (to quote Prof. Morris) there is a series of cream-coloured marly limestones, as well as oolitic rag-stones of some thickness (about 75 feet), as seen in the quarries near Stamford, where they yield the so-called 'Stamford Marble.' They occur also at Barnack (Barnack Rag1), Casterton, Geeston, Ketton (freestone 2), Collyweston and Morcot, Denton, Ponton, Corby, Weldon, &c., where they furnish valuable building-stone.
The beds contain, among Mollusca, Nerinca cingenda, Ceromya Bajociana, Pholadomya fidicula, Pinna cuneata, Mytilus Sowerbyanus, Astarte elegans, Pecten pumilus, Terebratula submaxillata, &c.; also the Plants Pecopteris, Pterophyllum, and Palaozamia.
These, together with the Collyweston Slates, are placed on the horizon of the upper part of the Inferior Oolite by
1 The Barnack Rag is said to have been quarried by the Romans, and the quarries exhausted four hundred years ago. (Sharp.)
2 The Ketton Stone was used in the construction of Peterborough and Ely Cathedrals.
Mr. Judd and Mr. Sharp. This position of the Lincolnshire limestone was first hinted at by the Rev. P. B. Brodie and Dr. Lycett.
In Lincolnshire (whence the name) the oolitic limestones which constitute the formation attain a thickness of about 200 feet: they thin out near Kettering. At Stamford the thickness is about 80 feet.
The beds are largely worked at Haydor and in the Railway-cutting near Grantham; also at Ancaster.
In the north-western part of Lincolnshire the Rev. J. E. Cross divides the beds as follows:
Lincolnshire Limestone, 36 feet.
Santon Oolites, with soft ferruginous bed at base.
Mr. Judd considers that the Lincolnshire Limestone was deposited under moderately deep sea-water conditions, but there are evidences in its lower portion of littoral accumulations. (See p. 172.)
The soil is light and not very productive. The beds, besides being largely used for building-purposes, are burnt for lime.
At Oundle and Higham Ferrers the Northampton Sand is directly overlaid by the Upper Estuarine Series (base of Great Oolite).
The term Fuller's Earth is applied to a thick deposit of blue and yellow clay, divided near the middle, in some localities, by beds of rubbly limestone, called Fuller's Earth Rock. It is characterized by the presence here and there of beds of blue and yellow Fuller's Earth, a sandy clay, which is described by Mr. Bristow as usually of a greenish-brown or greenish-grey colour, sometimes blue. It is opaque, soft,