The South Staffordshire Coalfield/Chapter 11
CHAPTER XI
Position and Lie of the Rocks.
Detailed Description.
The preceding chapter is intended for the use of the general geological reader, who wishes to gain merely a general notion of the structure of the district; read with the maps before him it may be sufficient for his purpose.
In this chapter it is intended to describe in a little more detail the features there sketched out, and to give some of the data on which the descriptions are founded.
We will first of all describe the main line of division before mentioned in Chapter X,. commencing with the northern part of it, namely, the Dudley and Sedgley anticlinal.
MAIN LINE OF DIVISION OF THE COAL-FIELD.
The Dudley and Sedgley anticlinal is not a simple one, but very complex. There is one general broadish area of elevation which may be said to be defined by the outcrop of the Thick coal. Ranged, however, on this wider and gently-elevated region there are three smaller areas that have each suffered from a maximum intensity of elevating force, namely. Dudley Castle Hill, the Wren's Nest, and the Sedgley district, including Hurst Hill. The axes of these three areas of Maximum disturbance do not run parallel to the general axis of the elevated tract, but cross it very obliquely, running nearly true north and south. They would thus appear to be the result of the nearly equal action of the two prevailing lines of disturbing force before mentioned, as they run in a direction equidistant between them.
Dudley Castle Hill.—At Dudley Castle Hill the two bands of limestone rise boldly out on the south, at angles varying from 25° to 30°, curve round with great symmetry and regularity on each side, and stretch off to the north in a narrow ridge, the sides of which dip east and west respectively from its central portion, see Fig. 18. As they run north the inclination of the beds increases to 50°, and the two pieces of the lower limestone nearly meet each other on the crest of the ridge. On the east side the limestones begin at Shirts Mill to curve regularly round towards the north-west, dipping north-east, and then towards the west, dipping north at 10°, but are then suddenly cut off by a fault. The limestones on the west side are cut off by a fault opposite Shirts Mill, and in the gap between these two ends a piece' of the upper limestone only is seen at the surface of the ground, dipping about west-south-west.
Fig. 18.
Scale, 2 inches to a mile.
Dark part is Coal-measure ground, with dark lines for coal crops; the part obliquely shaded being above the Thick coal, that horizontally shaded being below it.
Light part Silurian ground, with the limestones. Dotted lines are faults.
On the east side of the Castle Hill, between it and the Tipton road, the beds of limestone, after dipping from the hill for some distance, are found in the under-ground workings to flatten, and afterwards rise again towards the east, so that where the words "Castle-foot pottery" stand in the Ordnance map, east of the Tipton road, the limestone is reached by a shaft at the depth of only 52 yards (156 feet). From this point it again dips towards the east, at such an angle that in the space of 90 yards due east it becomes 112 yards deeps (336 feet).[1]
Wren's Nest Hill.—The Wren's Nest Hill is similar in general structure to the Castle Hill, but differs from it in some of its details. Like the Castle Hill, its general form is that of an oblong dome-shaped elevation, with a central nucleus of lower shale, on which repose the limestones, dipping every way at considerable angles from the centre of the hill. On the south-west side of the hill the beds curve round very symmetrically, dipping west, south-west, and south, at an angle of about 40°. Similarly on the north-east side the two limestones are symmetrically curved, dipping east and north-east, and finally almost north at about 45°. Along the east and south-east sides of the hill, however, the inclination of the beds is much steeper, rising to 50°, 60°, and in one part upwards of 80°. At the south-east corner the beds, instead of bending regularly round, are broken through by a fault, so that the end of the upper limestone on the west of the fault is made to abut against the base of the lower limestone on the east side of it. The lower limestone of the east side is itself cut off by the fault a little farther south, but the upper limestone ranges some distance to the south alongside of the fault till, being finally traversed by it at a very oblique angle, it also disappears. The course of the fault towards the north may be traced a little way by the ending of the lower limestone on its west side, but it very likely runs up to the centre of the hill. From this spot a fault runs due east, cutting through the beds on that side of the hill, and shifting their outcrop 30 yards, so that the upper limestone on the south side of it is made very nearly to face the lower limestone on the north; from which it follows that this must be a very considerable downcast to the south, the beds north of it rising at an angle of 55°, those to the south at one of 80°.
Fig. 19.
Caverns, West Side of Wren's Nest.
About 250 yards north of this another east and west fault cuts right across the ridge, fracturing the beds on the east side, and entirely cutting off those on the west.[2] From the centre of the ridge where it is traversed by this fault another is supposed to spring, running north-west, in order to account for the sudden ending of the two limestones in that direction as they curve round from the north-east side of the hill. Between these two last faults, on the north-west side of the ridge, a piece of the upper limestone only reaches the surface, just as a similar piece did between the two faults on the north-west end of the Castle Hill.
In the valley between the Wren's Nest and the Castle Hill repose the lower beds of the Coal-measures, the Bottom coal running some distance into it, both from the north and south ends of it.
Coal-measures likewise stretch between the Wren's Nest and the Sedgley Silurian district, but these are only the sandstones forming the base of the formation, and they lie only on the higher parts of the ground, the bottom of the valley north-west of the Wren's Nest showing Silurian shale at the surface.
The Sedgley District is rather a complicated one.
Hurst Hill.—On the east side of it is Hurst Hill, where the Wenlock and Dudley limestones rise into a long oval anticlinal ridge, like those of the Wren's Nest and Castle Hill, but not so perfect. At the southern end the two limestones bend round and abut against the base of a piece of the upper limestone, a fault running between the two; this piece of the upper limestone must be cut off each way by faults, and a fault dropping down to the west runs along the whole of the remainder of that side of the ridge, preventing the appearance of the limestones. On the eastern side the beds strike north, dipping cast at a high angle, they are broken through by a small east and west fault just south of the Cann Lane road, but from that spot strike still north till they curve round the northern end of the ridge, and dip in that direction.
They have been followed under ground north of the hill for 200 or 300 yards, dipping generally north at about 30°, and ending towards the west against a fault which runs about north-north-west, and which must be a downcast to the west.
Sedgley Beacon.—West of Hurst Hill is a rising ground formed of the Ludlow rocks, containing the band of limestone before described as the Aymestry and Sedgley limestone. These at first dip west at an angle of 10° to 20°, forming a pretty bold escarpment towards the east known as Sedgley Beacon Hill. The limestone, however, soon rises again to the west, and forms a cap to the high ground south of Sedgley, and after undulating a little in various directions, finally crops out on the west side of the hill, dipping cast at 10°. North of Sedgley this cap does not appear, the Silurian beds forming a basin instead of a cap, and only cropping out on the west side of the Wolverhampton road, where they dip pretty regularly to the east at an angle of 20° for about half a mile. 'They then appear to curl over for a short space, and dip north-west at 35°, but I believe this is only a local flexure, and that the limestone beds curve round from this point to meet those of the Beacon Hill quarry. About one third of a mile north of that, however, the limestone again appears suddenly at the surface, dipping north-east at 60°, its northern end curving round till it dips north and north-north-west, at 15° and 20°, and then suddenly ending. 'The faults drawn on the map are the most obvious explanation of this peculiar position of the rocks, though with the exception of the one on the west side of Hurst Hill, they are all put in hypothetically. In the hollow of the Silurian rocks north of Sedgley the sandstones forming the base of the Coal-measures again occur, as shown on the map. About half a mile south of Sedgley the Silurian rocks must be cut off by an east and west fault, a downcast to the south, which brings in the Coal-measure sandstone on their level.
Turner's Hill.—These lower sandstones spread over the ground from Upper Gornal, by Ellows Hall, to Lower Gornal, undulating in various ‹›directions, and at Turner's Hill, west of Lower Gornal, a patch of the Silurian with a band of Aymestry limestone again makes its appearance from under them. There is, however, but one small quarry in it, and the exact details of the structure of the country just hereabouts are very obscure.
Coal, supposed to be part of the Thick coal, has been found and partially worked in the valley, which runs from the west side of Sedgley down by Cotwall End. It was, however, much broken and disturbed, but was said to dip generally to the west, and frequently at very high angles.
At Sedgley Hall farm a trial pit was sunk in 1828, in which they passed through 120 feet of "red croprash rock and marl," under which were 200 feet of Coal-measures, and then the Thick coal dipping west at an angle of 12°. As there is no sign of the Thick coal cropping out between this spot and the Silurian ridge, there must be a fault between, which makes it probable that a fault forms the west boundary of the whole of the Sedgley Silurian district.
Outcrop of the Coals round the Dudley and Sedgley anticlinal.— We will now briefly trace the outcrop of the coals round this singularly dislocated district of elevation. Beginning on the south of the town of Dudley, the Thick coal and the beds just above and below it crop regularly out, dipping south at an angle of about 25°. The crop of the Thick coal may be traced very easily, partly by the old, partly by the present workings across Dixon's Green, and a little north-west of the Freebodies to Burnt Tree, when it dips east at 30°, and thence curving round the Silurian tract of the Castle Hill to the angle between it and the Wren's Nest. Along the north-east flank of the Wren's Nest the Thick coal is nearly vertical, and was worked in an open quarry in the years 1849 and 1850.[3] The coal strikes regularly from this spot to the Foxyards, where it flattens very rapidly to a nearly horizontal position.[4] It was formerly worked here also in an open quarry. Hence, after bending a little into the hollow between the Wren's Nest and Hurst Hill, the crop of the Thick coal runs along Ettingshall lane nearly up to Monmore Green.
A little south of Catchem's Corner it is broken through by the branches of the Great Lanesfield fault, which traverse likewise the lower beds to tle west of it. Here, between the Ettingshall Park farm and Monmore Green, there is a very broken and disturbed district of Coal-measures. It appears that a rude anticlinal curve runs north from Hurst Hill by Ettingshall Park farm, the Parkfield furnace, and the Rough Hills colliery. The New Mine. Fire-clay, and Bottom coals, after rising to the west, flatten, curve round, and dip again to the west; and a fault running north and south by the Wolverhampton furnaces, has a downcast to the west of about 150 feet, and brings in a good sized patch of the Thick coal in that direction, which dips north- west and west at an angle of 30° towards the red rock of the Permian formation. South of this, on the west side of the Parkfield colliery, the Coal-measures are completely smashed up by faults, and contorted in so violent a manner that, as J was informed by Mr. Smith of the Priory, one shaft passed through the Blue-flats ironstone three several times, first meeting it with the top bed uppermost, but dipping at a very high angle, then with the bottom part uppermost, also at a high angle, and then again with the top side uppermost and nearly horizontal, the beds being curved into the form of an S. It was quite impossible to represent on the very inefficient scale of the Ordnance map anything at all approaching to the complicated faults and contortions of this piece of ground; but a few of the principal have been drawn with a tolerable approach to accuracy. They show that the action of the disturbing forces did not end merely in producing the Silurian elevations lately described, but was continued into the Coal-measures to the northward, and may have extended still farther for an unknown distance, producing fractures and dislocations in rocks now buried under the Permian and New red standstone rocks on the north-west.
Returning now to the south of Dudley, the outcrop of the Thick coal may be traced by the old workings along the south-west side of the town up to Shaver's End and Russell's Hall. It dips at a gentle angle to the south-west, not exceeding in any case 20°, and rarely so much as 10°, and as the ground likewise slopes rapidly in that direction, the Thick coal does not at first acquire any great depth, and its outcrop is deeply waved and indented by the valleys and hollows of the surface.
Thus the little valley north of Russell's Hall completely cuts down through the Thick coal into the lower measures. As the ground on the opposite side of the valley, however, called Dipdale Bank, rises to 8 sufficient height, it again brought in a large patch of Thick coal that extended nearly up to Gornal, where the ground slopes the other way. This piece of Thick coal being in no place more than 20 yards deep, has long been worked out.
The Russells Hall fault.—On the south-west side of this indented outcrop[5] of coal runs the long Russell's Hall fault, which here throws down the Thick coal and other measures 120 feet to the south-west. Owing to a local flexure and rise of the beds, however, the Thick coal again crops out round Gornal Wood on the downthrow side of the fault.
The Russell's Hall fault running on the south-south-west side of the Sedgley and Dudley ridge, is continued to the south-east along the south-west flank of the Rowley Hills. It holds its course very regularly towards the south-east, its "throw" increasing as we proceed to the southward, up to 150, 180, and 240 feet, and eventually, near Rowley Regis, it has a downthrow to the westward of upwards of 400 feet. Beyond this its details are not accurately known, but at Coombs Wood it was partly proved by Mr. W. Mathews, and it seemed as if the fault were there passing into a very sharp anticlinal curve, a3 he found some Thick coal on the west side of it only 16 yards from the surface, and dipping at a high angle to the west, in which direction it acquires a depth of 750 feet in the space of a mile. On the east of the fault line it is known also to be 570 feet deep at a similar distance.
Near the foot of Mucklow Hill, a disturbance, probably due to this fault, may be seen in the Coal-measure sandstones, which dip 3° to the east on one side of it, and 30° or 40° to the south-west on the other. As the beds seem nearly, if not quite similar, it is probable that here also it is rather a rude anticlinal than a clean-cut fracture or fault.
The Rowley Basalt.—It is remarkable, that where the Sedgley and Dudley anticlinal ends, the mass of the erupted basalt of Rowley begins, and that hereabouts the Russell's Hall fault has its greatest amount of " throw," and is most of an actual fracture, while a mile south of the Rowley basalt the dislocation appears to be on the point of passing again into an anticlinal ridge. This almost looks as if there would have been a continuous anticlinal elevation all the way from Sedgley to the south end of the Lickey had it not been for the eruption of the Rowley rag. If the eruption of the Rowley basalt could be shown to have been subsequent to the formation of the whole Coal-measures, and contemporary with the fractures and dislocations of the coal-field, it might readily be accepted as a vera causa for the gap between the two anticlinals mentioned above. We should then suppose that the strain acting on the beds was relieved at one point by the actual outburst of trap, while in others it resulted in the uplifting and protrusion of the inferior rocks.
I believe, however, that this apparent connexion between the occurrence of the Rowley basalt and the dislocations and lie of the Coal-measures is an apparent and accidental one only. The change from a bold anticlinal to a mere depression, with a fault on one side of it. I think is due to the fact of the Dudley Port Trough faults cutting across the course of the anticlinal. These faults actually dislocate the Rowley basalt, which must, therefore, have been solid at the time of their formation.
It is, however, quite possible that the existence of the Rowley basalt and of the net work of dykes and veins of trap below it, was one of the reasons why the Dudley and Sedgley anticlinal was not continued to the south-south-east. The rocks beneath the basalt may be so bound and laced together by this net work of trappean braces, that the forces of elevation, whatever they were, were unequal to the task of bending them up into symmetrical curves and dome-shaped elevations like those of the Castle Hill and the Wren's Nest, &c., and left them, , therefore, comparatively undisturbed, except by fractures and dislocations, some of which we can trace, but of which many more probably exist than we are yet aware of.
I believe, therefore, that here, as elsewhere, wherever I have had an opportunity of making accurate observations, the mere intrusion or outburst of igneous rock has had little or no immediate connexion with the dislocations or elevations of the rock.
Following the direction of the line of the Russell's Hall fault south of Mucklow Hill, we find an interval of several miles in which no observations can be made.
What may be the position of the Coal-measures below the Permian beds of Frankley Hill we of course have no means of ascertaining; but on the south side of that ridge a few Coal-measures with a little coal showed themselves, on each side of the quartz range of the Lickey, in a nearly horizontal position. These beds may stretch continuously and horizontally under the Permian, from the valley south of Halesowen, and become exposed at the Lickey by simple denudation, in which case they are probably very high Coal-measures, or they may be the lowest Coal-measures brought up either by the rise of the beds or by dislocations concealed under Frankley Hill.
The Lickey Hill anticlinal.—If, however, we follow the direction of the southern half of the Russell's Hall fault, namely, about south-south-east, we shall strike in about 4 miles on the linear elevation of the Lickey quartz rock, which likewise has the character of a broken anticlinal. This fault, therefore, connects, if only in a vague way, the two anticlinal ridges of which the axes both run north-north-west and south-south-east, that, namely, of Sedgley and Dudley with that of the Lower Lickey.
The quartz rock of the Lickey is greatly broken and fractured, and in some cases violently contorted. At the northern end, about Holly and Rubury Hills, and by the New Road, it dips easterly at from 10° to 20°. Near the old Rose and Crown it dips west at 35°. In the quarry opposite the Reservoir it is violently contorted. At the south end limestone was formerly got, and there seem to be some softer shaly beds thereabout, which are doubtless the bottom beds of the Wenlock shale. It is believed that the eastern boundary of the quartz ridge south of the Colmers is a fault, with a downthrow to the east. North of the Colmers soft shaly beds, with calcareous bands and Silurian fossils, have been got on each side of the ridge, just underlying the Coal-measures.
We have doubtless here the very same beds that occur about Shustoke Lodge and near Hay Head, namely, the Llandovery sandstone locally altered into quartz rock and thrown into a small anticlinal ridge, with the bottom beds of the Wenlock shale and calcareous bands representing the Barr limestone covered unconformably by thin skirtings of Coal-measures. The Permian beds near Barr seem to be brought in solely by a fault, though perhaps even that is doubtful, while at the Lickey there is no occasion for any such supposition, since they seem simply to have covered up all the other rocks unconformably, and to be now partly removed from off a certain space by simple denudation.[6] The following diagram. Fig. 21, represents the probable relations of these rocks.
Fig 21.
Diagrammatic Section across the Lickey, through the Long Wood, and by the new Rose and Crown.
Scale, horizontal, 2 miles to 1 inch.
Nr New red sandstone.
Pt Permian trappean breccia.
P Permian red sandstones and clays.
C Coal-measures.
W Wenlock shale
L Llandovery sandstone converted into space in the centre.
THE SOUTH-WESTERN PART OF THE COAL-FIELD.
Having described the line of division which separates the south-western from the central portion of the coal-field, let us now examine the lie of the rocks in that south-western portion.
It was shown in the last chapter that this was partly separated into two basins by the Netherton anticlinal.
The Netherton anticlinal.—A little east of the village called the Lye, near Stourbridge, is found a protruding mass of Ludlow shale, with a band of limestone like that before noticed at Turner's Hill and Sedgley. It dips east at 40°, but after running north of the road for almost a quarter of a mile, it suddenly ends, being probably cut off by a fault. Immediately south of the road it terminates somewhat in the same way.
In the cutting of the road the Silurian shale may be seen dipping east at 40° for about 30 yards above the limestone; there are then 9 yards of Coal-measure sandstone, with ironstone balls, dipping in the same way, and 100 yards east of that the bottom beds of the Thick coal may be seen dipping west at 65°, or towards the limestone. The Thick coal must, therefore, be reversed, or bottom upwards. In the Hays coal-pits, just east of this, the Thick coal is found greatly broken and disturbed, dipping generally east, at a high angle, and then suddenly assuming a nearly horizontal position, in which it continues some hundred yards to the eastward.[7]
From the Hays the crop of the Thick coal may be traced about a quarter of a mile to the south-south-west, when it curves suddenly to the west, dipping south at a considerable angle. On the other side of the Lye the Thick coal comes in again dipping west, and on this side the outcrop of the coal may be traced some distance to the south-west, when it appears suddenly to come to an end.
In the brook between these two terminations of the Thick coal some Coal-measures may be seen dipping to the south, it is, therefore, very probable that the apparent termination of the Thick coal outcrop te the south-west of the Lye is due merely to a sharp flexure and change in its strike, and that it turns suddenly to the eastward and joins that coming towards it from the other side of the anticlinal. The Netherton anticlinal will in this way terminate to the south with a regular sweep of the beds across the direction of its axis in the same way that it ends to the north.[8]
From the Lye to Netherton church the anticlinal runs very steadily to the N.N.E., the Thick coal dipping on either hand at an angle of about 20° to 25°, and its outcrop quite easily traceable by the old workings. Just north of Netherton church the anticlinal dies away, the two outcrops meet, and the Thick coal dips north till it flattens and rises again towards Dudley.
In the centre of this anticlinal, in the canal tunnel and cutting near Yew Tree Hill, is exposed a remarkable mass of basalt or greenstone which sends out veins into the adjacent Coal-measure sandstone, and is therefore intrusive. It is not at all necessary, however, to look upon the intrusion of this mass of trap as contemporaneous with the formation of the anticlinal elevation.
The Cradley Basin.—It appears from former and recent information that a fault runs parallel to the Netherton anticlinal on the eastern side of it, from Careless Green to the neighbourhood of Musham. I believe this fault, however, to be merely a fracture, with but a slight displaces ment, in the Thick coal and other measures where their "lie" changes suddenly from a nearly horizontal to a highly inclined position.
From this line of disturbance they appear to stretch across very uniformly and nearly horizontally under Cradley Heath. Congreaves, and High Haden, as also under Dudley Wood and Old Hill, till they reach the Russell's Hall fault before described, when they are suddenly bent up at a sharp angle as well as broken and heaved to a height of 300 or 400 feet.
A few small faults are met with about Baremoor and Congreaves, as shown on the map, and another small east and west fault runs through the Hawn Colliery with a downthrow of 30 feet to the south.
As the beds dip to the south, while the ground rises rather rapidly in that direction, it follows that the uppermost beds of the Coal-measures must soon make their appearance. We accordingly find the Halesowen sandstone group stretching across the coal-field from east to west, and above those we soon meet with the red beds of the Permian formation.
On the road from Halesowen to Hagley two considerable patches of Permian rock are seen to rest on the upper sandstones of the Coal-measures; one at Quarry Hill and Hasbury, and the other at Hayley Green. These Permian beds dip to the southward; but in the brook immediately south of them good Coal-measure beds can be seen, and farther south in Uffmoor Wood one, if not two, little coals have been found, and may be seen cropping into the brooks. It is clear, therefore, that these two Permian outliers are cut off to the southward by a fault which is an upcast to the south, and runs about east-north-east and west-south-west along their southern boundary.
The southern boundary of the coal-field stretching from Wychbury Hill on the west, to Lappal tunnel on the east, is formed by the horizontal beds of the upper Coal-measure sandstones and shales becoming covered as we ascend the rising ground to the south, by the horizontal beds of the Permian rocks.[9] It will be seen accordingly, by inspection of the map, that this boundary, instead of being smooth and regular, like that of the east and west sides of the coal-field, is indented and undulating, depending chiefly on the shape of the ground. Wherever a valley sufficiently deep penetrates to the south, there is a bay of Coal-measures marked in the map. Wherever a ridge sufficiently high stretches to the north, a promontory of red rock will be seen advancing in that direction. We have here, therefore, a true natural surface boundary of the coal-field, caused simply by the irregular denudation of the rock that covers it.
Pensnett Basin.—The Pensnett Basin is bounded by the Netherton anticlinal on the south-east, the south-western slopes of the Dudley and Sedgley ridge, and the northern part of the Russell's Hall fault on the north-east and the Western Boundary fault on the north-western and south-western. Instead of declining gently to the north and passing under the Permian, as in the Cradley basin, the beds of the Pensnett basin rise and crop out to the south, not only along the flanks of the Netherton anticlinal, but over great part of the ground between it and the Boundary fault.
Immediately west of the Lye, indeed, there is a little basin of Thick coal which under the Grange is at a depth of 140 yards, and seems to dip thence rapidly southwards towards Prescott, as was before described, when speaking of the south end of the Netherton anticlinal. It not only dips south, however, but rises rapidly towards the west at an angle of 45°, and cropping against the boundary fault for some distance it reaches the surface just south of the Stourbridge road, whence this outcrop strikes north-easterly, and runs parallel to the Netherton anticlinal for some distance, thus making the little trough of Hay Green and Tintam Abbey.
The Thick and other coals, however, are so much deteriorated here by "rubbish" that the clays become the more valuable mines, especially the Fire-clays used for making the well-known Stourbridge fire-bricks.
After striking north-easterly up to Mousehall farm the crop of the Thick coal then curves to the west towards Amblecote, and runs in a curved line to the boundary fault a little south of Brettell Lane, as shown in the map. All along this line the dip is to the north under Brierley Hill.
A few little east and west faults traverse the Amblecote and Hay Green district, and are said to extend even across the anticlinal.
Fig. 22.
Brierley Hill Trough Faults.
Scale 6 in. to 1 mile, vertical and horizontal].
1. Upper Sulphur coal.
2. Two-foot coal.
3. Broach coal„
4. Herring coal„
5. Thick coal.
6. Heathen coal.
7. Silurian shale.
Brierley Hill Trough Faults.—At Brierley Hill two much more powerful dislocations form a trough, each having a downthrow of 80 or 90 yards (or about 250 feet), in the centre of their range, but decreasing that amount towards their extremities to less than 30 yards (or 90 feet). The southern of these two faults ends on the west flank of the Netherton anticlinal, but the northern one is said to run right across it, carrying a downthrow to the south of 10 or 12 yards, and running in a curved line to Withymere, where it dies out on coalescing with the Russell's Hall fault.
Brockmoor Fault.—On the west both these faults are cut off by the southern end of the Brockmoor fault, which, springing out of the western boundary fault north of Brettell Lane, runs about north-northeast to Pensnett reservoir, having a downthrow to the west of about 300 feet. This fault sends out two slight branches, one to the east by the Round Oak, with a downthrow to the south of 5 yards; one to the north-east through Hart's Hill, with a downthrow to the south of 10 or 8 yards. At Pensnett reservoir the Brockmoor fault is believed to branch as shown in the map.
I was informed by Mr. Pearson, of Brierley Hill, that "at Brockmoor this fault threw down to the west 130 yards, or nearly 400 feet, that it was only a slip, but was 200 yards wide, or made that much barren ground." The meaning of which description is, that although the fault itself had no apparent thickness, yet the two ends of the Thick coal were separated by 200nbyards measured on the surface of the ground, showing the fault to have an inclination of not more than 33°.
Corbyn's Hall Fault—The Corbyn's Hall fault strikes out of the Great Boundary fault about a mile north of Bugpool, a little west of Salter's Hall. Its downthrow is likewise to the west and north, at first 360 feet, diminishing then to 300, which it maintains for upwards of a mile. It then curves gradually round to the north-east by Shut End House, diminishing its throw to 240 feet, and thence passing through the north end of Barrow Hill by Hunt's Mill, it strikes east up to Russell's Hall iron furnaces, its downthrow being north 120 feet. I believe this is the fault mentioned by Sir R. I. Murchison in the Silurian System, p. 504. He gives a section of it on the authority of Mr. W. Mathews, in which there is an actual dyke drawn, 140 yards in width, between the broken ends of the coal. Mr. Mathews derived his information from his ground bailiff of that time, but on cross-questioning his present ground bailiff. Mr. Job Taylor. I arrived at a different and more natural explanation of the facts. I may premise, that in South Staffordshire, by the "width" of a fault is always understood the width measured at the surface of the ground, between the broken ends of the Thick coal, or any other bed that may be worked. It is the space of barren ground as to that particular bed, the width of which is measured in yards on the mining plan. It depends, therefore, not on the actual or real width of the fault, but solely on the angle of its inclination. This will be seen from the following account:—Job Taylor first assured me that this was not a fault at all, but only a slip, by which he meant that there was no real width or substance in the fault. He then told me that the "throw" of the fault was 90 yards, and its "width" was exactly the same, as in the following diagram (Fig. 23):-—
Fig. 23
Scale, 1 inch= 150 yards.
A. B. C. Shafts.
D. Gate-road.
1. Beds containing water.
2. Brooch coal.
3. Thick coal.
4. The fault.
A shaft (A in the diagram) was sunk, which crossed the fault between the ends of the pieces of Thick coal, and was therefore said to be sunk in the fault. But from this shaft they drove out a gate-road (D), and on the deep side they hit the Brooch coal in advance of the Thick coal, as in the diagram. Moreover, there were certain wet beds (1 in diagram), beds from which water came out, above the Brooch coal. Now, in a shaft (B) sunk to the Thick coal on the crop side of the fault, these beds were not passed through, and the shaft was quite dry; while in the shafts (C) farther from the fault, they were met with, and the shafts were quite wet. This likewise agrees with the diagram, and the facts are explicable only on the supposition of its correctness. Job Taylor likewise assured me that on the deep side of the fault the coal was "pinched" towards the fault by the descent of the roof, as in the diagram. If the reader will draw perpendicular lines from the ends of the Thick coal No. 3, where they are traversed by the fault, up to the surface, the space between those lines will give him the width of the fault according to the common notions of it.
Shut End faults.[10]—A little north-west of the commencement of the Corbyn's Hall fault, two parallel faults strike nearly north from the Boundary fault near the Standhills, one throwing down to the west about 300 feet, another up to the west 150 feet, with a complicated and broken piece of ground between them. They coalesce or come very near together, just south of the Dudley and Kingswinford turnpike road, and thence proceed as one fault north-by-east, just west of the Shut End furnaces, with a total downthrow to the west of 180 feet. This fault, called the Shut End fault, is believed to run by Askew bridge up to the Russell's Hall fault there.
Tansy Green Trough.—It sends a considerable branch from Shut End by Cooper's bank, nearly to the Graveyards, which has a downthrow to south-east of about 120 feet. This branch forms a trough with the northern or north-eastern extension of the Corbyn's Hall fault, both running nearly east and west, and having a downthrow of about 90 feet towards each other.
Even at Shut End the fault is not a single fissure, like the Corbyn's Hall fault, but a wide dislocation made up of a number of steps or smaller fractures (see Horizontal Sections. Sheet 25, No. 7). Mr. Colly, the ground bailiff, was kind enough to give me the details of a gate-road that was driven through the fault, starting from the Thick coal on the "crop" side of it, i.e., the upcast side. The gate-road was horizontal, but they met, in driving, with beds lying at various angles, of which the following are the details:-—
| FT. | IN. | ||
| 1. | Coal and batt | 9 | 0 |
| 2. | Rock binds | 42 | 0 |
| 3. | Rock | 12 | 0 |
| 4. | Peldon | 21 | 0 |
| 5. | Rock binds | 33 | 0 |
| 6. | Pin measures | 12 | 0 |
| 7. | Herring coal | 6 | 0 |
| 8. | Bind measures | 9 | 0 |
| 9. | Brooch coal | 34 | 6 |
| [11]10. | Rock binds | 8 | 0 |
| 11. | Herring coal | 9 | 0 |
| 12. | Bind measures | 9 | 0 |
| 13. | Brooch coal | 9 | 0 |
| 14. | Fire-clay | 9 | 0 |
| 15. | Two-foot coal | 6 | 0 |
| 16. | Red ground | 33 | 0 |
| 261 | 0 | ||
This red ground No. 16 was outside of the faulty ground, and at the end of the 33 feet they sank a "jackey pit," and found the Two-foot coal which they had just previously passed through lying horizontally 22 feet below them. The whole length of the gate-road was 261 feet, during which they twice passed along the same set of beds, rendering it probable that there was an upcast between the downcast faults. Had the dip of the several fragments of beds been given, we might have constructed a very instructive section of this gate-road.
Gornal Wood faults.—Between Gornal wood and the Graveyards there are four faults which strike south-south-west out of the Russell's Hall fault, each having a downthrow of 21 feet to the east-south-east.
It will be seen that not only these, but the other principal faults, namely, the Shut End. Corbyn's Hall, and Brockmoor faults, have likewise a general bearing of north-north-east and south-south-west where their throw is greatest and most decided, and that where they deviate widely from that bearing is where they send out branches that eventually become east and west faults, or where perhaps such faults merge into them,
These east and west faults have generally a less amount of dislocation than the others, the only large throws being in the pair of faults that make the Brierley Hill Trough, and these are only important with respect to the piece of ground which lies between them.
The general effect of the three great north-north-east and south-south-west faults, the Brockmoor, the Corbyn's Hall and the Shut End, is to throw down the measures towards the west, and extend the coalfield in that direction. If it had not been for these breaks it seems likely that the outcrop of the Thick coal south of Brettell-lane might have run in a straight line north-north-east for that north of Turner's Hill by Cotwell End and Sedgley Hall farm.
If the coal had not cropped out along that line, it is at all events very probable that the western boundary fault would have run along it with one great heave of a downthrow to the west bringing in the Permian or New red sandstone beds against the Coal-measures.
Instead of one great heave, we may look upon these three faults as subdivisions of the boundary fault, letting down the coal measures by a succession of steps towards the west before burying them under the other formations.
Between Netherton and Dudley the two basins of Pensnett and Cradley coalesce, the coals and the principal dislocation,—the Russell's Hall fault,—ranging uninterruptedly from one to the other, and the beds dipping north from the end of the anticlinal till they rise to the Russell's Hall fault.
THE CENTRAL AND NORTHERN PART OF THE COAL-FIELD.
We now come to the part of the coal-field which lies east and north of the main line of division. Before describing the position of the Coal-measures, however, it will be as well to give an account of the Walsall Silurian district and show the connexion between the beds there and those which have been already described as appearing on the Dudley and Sedgley anticlinal.
The Walsall Silurian district is of very irregular shape, owing partly to the action of several faults, partly to the overlapping of the _Coal-measures. In the cutting of the South Staffordshire railway on the west of the town may be seen the calcareous beds of the upper or Little limestone. They dip west at an angle of 5°, and in that direction the Silurian shale becomes shortly covered by the lower Coal-measures containing the Blue flats and other ironstones. On the north of the town, and east of the Lichfield road, are some large old quarries, in which the lower or Thick limestone was formerly worked, dipping westerly at 10°. This limestone must be continued under the town to the southward, being concealed from view by a very thick capping of quartzose gravel of the Drift period. Just south of the town it must be cut off by the fault which runs east and west from the south side of "the Moat." This fault is known in the Coal-measures to have a downthrow to the south of 120 feet. Its extension to the east is partly hypothetical, as from Walsall race-course no rock is seen at the surface either southward or eastward for at least a mile and a half.
In tracing the Thick limestone to the north it is seen to bend round and to be cut off by a small fault, a downthrow to the north, near "the Butts." Partly by reason of this downthrow, partly from the rise of the ground, the lower Coal-measures with the Blue flats ironstone here overlap the limestone, and run some distance to the east of its outcrop, till the gradual fall of the ground allows the Silurian shale to come to the surface again.
Near Rushall Castle is another little fault throwing down to the north, but here the Thick limestone again crops to the surface, in consequence of the denudation of the Coal-measures, and has been worked in quarries towards the north-east as far as Linley. In some of the quarries between Rushall Castle and the Halfway House the Coal-measures may be seen on the west side of the excavations resting on the Silurian shale; but the Coal-measure boundary shortly strikes north, while the Silurians strike north-west, in consequence of which at Daw End the Upper or Little limestone comes out from under the Coal-measures, and may be traced by a line of old quarries running in a curved line down towards Ketton's garden. In the canal near here a small supplementary band of limestone is found between the two limestones, and towards the Halfway House a short band of limestone was worked below the Thick limestone. These masses are called "Self lumps;" they are large lenticular masses, in which the calcareous so far prevails over the argillaceous matter as to form good workable limestone.[12] North and east of Daw End the Silurian rocks are altogether cut off by a great fault, which we may call the Daw End and Linley fault, running north-west and south-east, throwing down to the northeast and bringing in the Coal-measures in that direction.
In this Coal-measure tract was sunk the Trial pit at Aldridge (see Vertical Sections. Sheet 16, No. 4), and another pit between Aldridge Lodge and Hill End. This latter pit. I was informed by Mr. Roberts of the Butts, was 62 yards deep, and that three measures of coal and two of ironstone were passed through, the whole dipping east-southeast at an angle of 25°.
Starting from the Walsall and Daw End limestones, and traversing the ground to the east, we find here and there small openings or cuttings in the shale below them, but we do not get much information till we come to the banks of the new canal running from Longwood Wharf south-south-west by Ginity Graves and the Bell to the Tame Valley canal that runs by Bustleholme Mill and Ray Hall. All down this canal are cuttings in Silurian shale or "bavin," for the most part as nearly horizontal as possible.[13] East of it, about Hay Head, we get another limestone rising from underneath this shale at an angle of about 10°, running from the fault near Aldridge Lodge down to Daffodilly, where it begins to curve and dip at a high angle, finally ending against the "red rock" near the Skip, its last piece dipping south-west at 35°. East of this, which is locally known as the Barr limestone, nothing is seen till we come to the "red rock;" but as near Hay Head there is a space of one third of a mile between the two, we ought, if this Barr limestone be truly the representative of the Woolhope limestone, to get the upper part of the Caradoc sandstone series in the intermediate space. The ground is absolutely flat, and rather wet and marshy, and apparently covered by drift clay, so that in the absence of deep excavations this point cannot be settled.
The above passage is left as it stood in the first edition, and it has been already pointed out, p. 109, that subsequent research proved the existence of this sandstone where it was thus anticipated, and showed that it was concealed not only by Drift clay, but by a thin covering of Coal-measures, except in one little ditch or gully at the back of the house called Daffodilly and in a small quarry near Shustoke Lodge. The sandstone, now called Llandovery, rises gently out from under the Wenlock shale, the relations of the beds being precisely the same as at the Colmers and the Long Wood near the north end of the Lower Lickey.
It is possible that the fault before mentioned, which strikes east and west from the Moat, and is supposed to cut off the limestones south of Walsall, is continued to the east, and likewise cuts off the south end of the Barr limestone.
No limestone is known, either by natural outcrop or by sinkings, south of this line. 'The Silurian shale, however, is seen at intervals, not only in the canal before mentioned but at other points, and was formerly exposed in the cutting of the London and North-western Railway south of Tame bridge. In a horsepond at the Goodwin farmhouse considerable nodules of limestone were got out in the year 1849, rendering probable the near neighbourhood of one of the bands of limestone to this spot. On Delves Green are many old pits in the lower Coal-measures, from which the Blue-flats ironstone had formerly been got, and one of these had been sunk as a trial pit to the depth of 50 yards, chiefly, as appeared from the "spoil" on the pit bank, in Silurian shale. Near the seventh milestone on the Walsall and Birmingham road an outlier of Coal-measures, with sandstone and ironstone, was cut through on the top of the high ground there, making it probable that the whole of this piece of Silurian shale south of the outcrop of the limestones would have been covered by a mask of Coal-measures, had the ground been a little higher and the rocks not worn down by denudation to their present level.
That the Silurian shale continues under the coal-field to the westward of the district now described, dipping gently and equably towards the west, is shown by the following facts:—
On the west side of Friar Park wood a shaft was sunk in 1849, in the first 60 feet of which one or two small coals were found, under which were some ironstones, and below them Silurian shale, in which the sinking was continued to a depth of 150 feet from the surface.[14]
At Hobbs Hole, a little cast of Darlaston, according to the section given at p. 108, from Mr. Smallman's information, there are 292 ft. 6 in, of Coal-measures beneath the Heathen coal, then 60 feet of Limestone shale, followed by the Thin limestone of Walsall, which is there 16½ feet thick; and at a depth of 90 feet below that the Thick limestone, which is there 30 feet thick.
At Bentley, south of Pouk Hill, the top of the Silurian shale was about 160 feet deep, and the Thin limestone 373. In the Chillington colliery near Wolverhampton they reached Silurian shale at a depth of 580 feet, and passed through shale and thin bands of limestone for more than 200 feet additional.
In addition to the above places where the Silurian rocks have been reached through the Coal-measures, we have at Deepfields the top of the Silurian shale 680 feet, and the top of the limestone 850 feet deep; at Dudley Port Silurian shale at a depth of 550 feet, the limestone at 620 feet; at the pits at Langley Green, south of Oldbury, a considerable thickness of Silurian shale passed through in a pit net more than 390 feet deep; and the same rock but a little way below the Thick coal at West Bromwich Heath pits.
If we look at these facts, together with that of the protrusion of Silurian rocks at Turner's Hill, the Hayes near the Lye Waste, and the Lickey, we are led irresistibly to the conclusion that a great floor of Silurian rocks stretches immediately under the comparatively thin covering of Coal-measures throughout all the coal-field south of Bloxwich at all events.
The central portion of the coal-field.—The central portion of the coal-field lies in the hollow or basin between the Silurian ridge of the Dudley and Sedgley anticlinal and the Walsall elevation.
If we take Tipton old church, the Moat colliery, and Princes End and that neighbourhood as a centre, the beds, being there deepest, rise thence gently towards the surface in every direction except towards the south. As they approach closely to the Dudley and Sedgley anticlinal they are bent up much more rapidly than elsewhere, the angle of inclination near that outcrop being in some places nearly vertical, and generally as much as 20° or 30°.
The beds rise more gently on the east towards the Walsall Silurian ground, at a mean angle of about 5° perhaps, but still more gently on the north, where the space between the outcrop of the Thick coal and that of the New mine coal is not less than two miles, although the vertical thickness between the two beds does not exceed fifty-six yards (or 170 feet). This gives a mean inclination of only about 1 in 62, or less than 1°. In the same way the Thick coal, when it does take the ground, between Wolverhampton and Bilston, declines so gently into it as never to be more than forty yards deep, and consequently never to be deep enough to take in the Brooch[15] above it for more than a mile to the southward, till it meets the Lanesfield fault. South of that district the measures in all the middle part of the central portion scarcely vary from a horizontal position. Notwithstanding the nearly horizontal "lie" of the beds over the greater part of the central and south-eastern district, the depth of any measure, as the Thick coal for instance, varies frequently. This variation is produced to a slight extent by the undulations of the surface, but chiefly by the upthrow or downthrow of the faults.
In describing the south-western district it was shown that the two basins into which it is divided were connected at the northern end of the Netherton anticlinal by a trough, which we proposed to call, from the name of some old ironworks therein, the Buffery trough. It is just here also, where the two anticlinals of Netherton and Dudley terminate, that there is the closest connexion between the south-west and the central portion of the coal-field. The Thick coal and other beds dip towards the Buffery trough, not only from Netherton, but also all along the south side of Dudley, whence it gradually curves round so as to dip first towards the Rowley Hills and then towards Tipton. The only thing, in fact, which separates the two districts here is the Russell's Hall fault, which is here a simple fracture and downthrow of about 150 feet towards the Buffery. If it were not for this dislocation the central and south-western districts would here become confluent, just as the Cradley and Pensnett basins become confluent.
Now it is from this neighbourhood that the most powerful and dominant fracture strikes into the central district, nearly parallel and almost in a line with the axis of the Netherton anticlinal. This fracture consists of the pair of faults which produce the Dudley Port trough.
At the time when the coal-field was first surveyed these faults were supposed to cease altogether on approaching the basalt of Cawney Hill. In the partial revision of the district, however, which I was able to make in October 1858, there appeared good reason for believing that they did not entirely cease, but that the basalt cf Cawney Hill was cut off on the north by the continuation of the north-western fault, and that it was partly separated from that of Tansy Hill by the opposite fault. It is probable, then, that the Dudley Port Trough faults do not entirely cease till they strike the Russell's Hall fault a little to the north-west of Gad's Green reservoir.
Now, it is very remarkable that a small fault proceeds from the northern apex cf the Netherton anticlinal obliquely towards the same part of the Russell's Hall fault. There seems, then, to be almost a direct connexion between the Netherton anticlinal and the Dudley Port trough.
If we produce the axis of the Netherton anticlinal it will strike exactly into the centre of the Castle Hill dome-shaped elevation.
I believe we have in these and similar facts a proof that the forces of elevation and disturbance which were acting on the country to produce the principal features in the lie of the rocks acted along lines running north-north-east and north-north-west, here one force and there another predominating, and producing N.N.E. or N.N.W. fractures or elevations accordingly, with occasional oblique connexions between two parallel and adjacent lines of effect. The two forces seem also to have been sometimes so equally balanced as to have their direction resolved into lines equidistant between them, and therefore running either north or south, as in the Castle Hill and the Wren's Nest, or cast and west, as in some of the large faults and dislocations. The north and south lines of course bisected their smaller angle of intersection, the east and west lines the larger angle.
Having dwelt long enough, perhaps, on what is believed to be the law governing the direction of these lines of disturbance. I will now proceed to describe those of the central district a little more in detail.
The Dudley Port Trough faults.—These are two parallel faults starting from near the Free bodies at the north-west corner of the Rowley Hills, and running about north-north-east for about 2 miles up to the Horsley collieries. They are scarcely a quarter of a mile asunder, and each throws down the piece of ground between them to the maximum depth of 130 yards; that is, the piece of Thick coal between them is 130 yards (or 390 feet) deeper than that on either side. (See Fig. 24.)
Fig. 24.
Dudley Port Trough Faults.
Scale 6 in, to 1 mile vertical and horizontal.
1. Upper Sulphur coal.
2. Two-foot coal.
3. Brooch coal.„
4. Thick coal.„
5. Heathen coal.„
6. New mine coal.
7. Fire-clay coal.„
8. Bottom coal.„
9. Silurian shale, with Dudley limestones.
From the maximum of 130 yards, however, the throw of these faults diminishes in each direction to one of much less amount. It has been proved by the workings that each of these faults hades, or slopes downwards, towards the other at an angle of about 70°, they must, therefore, meet at no great distance below the included piece of coal, and as their throw is equal and opposite, they must, where they meet, exactly counterbalance and neutralize each other, and if continued at all, must descend as a mere fissure or crack, without producing any dislocation. It so happens that the included piece of coal is, at Dudley Port, exactly on a level with the Dudley limestone outside the faults, and the workings have been continued from the coal into the limestone. This likewise shows that as regards the mass of the country on each side, these Dudley Port Trough faults (or fault) are no dislocation at all, but only so as regards the piece of ground between them. Nevertheless, it is probable that they mark the line of most intense strain at the period when the clevatory forces were acting on the district. This is a point which for convenience sake we will discuss more fully farther on.
That they had the effect of materially modifying the action of the disturbing force is shown by the fact that to the southward of the Dudley Port Trough all the faults are downthrows to the north, while to the northward of it all the faults are downthrows to the south; in other words, all the faults of the central district form no succession of steps down to the Dudley Port Trough faults.
Faults between Dudley Port Trough and Rounds Green.—Starting from Round's Green, between Timmin's Hill and Oldbury, we have 4 faults, with some branches, running about north-east and south-west, and throwing down to the north-west from 90 to nearly 180 feet. The course of these faults is concealed towards the south-west by the trap of the Rowley Hills, while towards the north-east they appear to die out, or at all events have not been traced. The southern fault of the Dudley Port Trough itself dies out towards the north-east, its throw diminishing to 210 feet near Horsley, where it has a small branch throwing down to the south 90 feet. Two small faults, with a southern downthrow, likewise start out of it near Roseland farm.
The northern fault of the Dudley Port Trough runs into and coalesces with the Tipton fault near Horsley.
North of the Dudley Port Trough we have 7 principal faults all running nearly east and west, and all having a downthrow to the south. These are (see Horizontal Sections. Sheet 23. No. 1)—
1. The Tipton and Hilltop fault.—This has a branch running from Tipton to the south-west, and throwing down 54 feet to the northwest; but its main line at 'Tipton Green throws down 45 feet to the south, and thence it runs about east-by-north to Hilltop, having a maximum throw of 150 feet to the south near the Eagle furnace, whence it diminishes in amount towards West Bromwich old church to 20 feet and less.
2. The Bald's Hill fault, which, just north of Mr. Davis's Crook Hay furnaces near Hateley Heath, has a downthrow to the south of 420 feet. This fault runs cast as far as Stone Cross, beyond which its course has never been proved.[16] To the west of Bald's Hill this fault splits into two branches, the southern of which runs through Gold's Green with a downthrow to the south of 96 feet; the other runs through Hocker Hill, its downthrow diminishing from 120 to 90, and finally to 25 feet, as it runs west.
3. The Coseley and Wednesbury fault, which in its central part has a downthrow to the south varying from 150 to 210 feet. To the westward it splits into two, each having a downthrow of 45 and 66 feet respectively, and then diminishing to nothing. On the south side of the town ot Wednesbury its throw is 90 or 105 feet, whence it runs towards Crank Hall, and probably dies out.
4. The Lanesfield fault, which has a downthrow to the south of 180 or 210 feet, near Hallfield, diminishing in each direction, and finally dying out. Towards the west this fault splits into two well marked branches, which have a throw at first of 105 and 66 feet respectively, the southern branch diminishing very regularly from 105 to 30 and 20 feet, the northern being cut off by one of those faults mentioned before as being very numerous and complicated in the corner of the coal-field north of the Sedgley ridge, and marking the prolongation of the disturbing power which produced the anticlinal.
5. The King's Hill fault is a very slight one, having a throw of not more than 20 to 25 feet to the south.
6. The Darlaston fault has just east of Darlaston a downthrow to the south of 66 feet. It is not known cast of that, but it may possibly run along the north side of Delve's Green, where the Coal-measures stretch eastwards over the Silurian shale. 'To the west it splits half a mile from Darlaston, its branches diminishing to 27 and 9 feet respectively, and shortly disappearing.
7. The Moat fault mentioned before as running south of Walsall. It has a downthrow to the south of 120 feet just south of the Moat, but nothing more is known respecting it.
Mr. George, of Bentley, has lately pointed out to me another fault a little south of the Moat fault, running parallel to it, and likewise having a downthrow to the south.
Several other small faults may also be seen marked on the map, not worth a more detailed description.
Outcrop of the Thick coal.—It will be worth while briefly to follow the outcrop of the Thick coal over the district thus broken by faults.
Its outcrop along the eastern flank of the Sedgley and Dudley anticlinal ridge has already been described (p. 149), and it has been shown how it is dislocated by the western branches of the Lanesfield fault, and that a detached piece was thrown in towards the Wolverhampton furnaces in consequence of other faults having a downthrow in that direction aided by a rude sort of anticlinal arch that occurs about Parkfield.
The outcrop then runs along the western side of Ettingshall Lane for some distance, and then turns across it and across the Wolverhampton and Bilston round toward Batchcroft and Priestfield. A small east-and-west fault, with a downthrow to the north, throws in another little detached piece towards Monmore Green. The outcrop runs thence very steadily about east by south to Darlaston, where it is broken by the Darlaston fault and partly deflected to the north by the rise of ground. Thence the outcrop runs south-east till it is broken and thrown forward to the east by the King's Hill fault, whence it runs south to the Lanesfield fault, which again throws it forward to the east. Thence it begins to run nearly south-west into the northern part of Wednesbury, "when it is cut through and thrown nearly half a mile to the east by the Coseley and Wednesbury fault. South of that fault it runs about south-south-west, and is deflected by the valley of the Wednesbury brook, south of which it meets the Bald's Hill fault. The outcrop is then thrown to the east more than a mile to Stone Cross, partly by the downthrow of the Bald's Hill fault, partly by the rise of ground, and partly perhaps by a flattening of the dip of the measures. From Stone Cross it strikes about south-south-west till cut by the extremity of the Tipton fault north-west of West Bromwich old church. This fault, however, is here very slight, so that the outcrop seems scarcely affected, but continues as far as the Hall End colliery. In this it meets with a fault running about north-east by north, which has a downthrow to the south-east. This would throw the outcrop still farther to the eastward, in which direction, however, everything is so covered by drift that its outcrop is not known. There then appears to be another fault ranging about north-east by east, having likewise a southerly downthrow, bringing in the red rock of the Permian formation, under which the Thick coal continues for some distance at a depth of 600 or 700 feet till it ends, either in a rock fault, an outcrop of the beds into the Permian rock, or against an upthrow fault. It is not improbable that the Thick coal terminates for a time, if not altogether, towards the east under the Permian rocks, in one or all three, of the methods alluded to above. From the south side of the Tipton fault, about two-thirds of a mile west of West Bromwich old church, a fault strikes off to the southward with a downthrow to the east, and runs thence through Oldbury to the Quinton. This will be described presently under the head of the Boundary faults.
The south-eastern part of the coal-field.—Between it and the Rowley Hills is the south-eastern portion of the district, in winch the beds appear to lie very regularly and horizontally, although the Thick and other coals are greatly injured by the quantity of sandstone interstratified with them, a3 before described. Such as they are, however, these beds appear to have been very little disturbed by fractures and dislocations, the debased representative of the Thick coal passing under the Rowley basalt on the one side and striking against the Boundary fault on the other at a depth of 400 or 500 feet, often thinning from 30 feet to 3 feet in all directions, and being frequently not worth the trouble of getting. South of Causeway Green and Cakemoor little or nothing is known either of the constitution or the "lic" of the Coal-measures, but they are believed to dip gently to the southward until they pass beneath the red rock found above the Lappal tunnel. These red rocks may be seen occasionally thereabouts to dip south at an angle of 5° to the south.
From the neighbourhood of the Lappal tunnel, however, it will be seen, by reference to the map, that a curious little narrow strip of Coal-measures runs out two miles to the east, as far as the Stone House near Harborne. The existence of Coal-measures at the surface along this strip is shown partly by the rubbish got out of the shafts of the tunnel near Wilderness Farm, but principally by a pit sunk by Mr. Flavel, between the Stone House and Bog Meadow Coppice. From this pit, which was 80 yards deep, nothing but Coal-measure shales and "binds," with small ironstone nodules, was extracted. The measures dipped north at about 10°, and they may possibly have dipped regularly under the Permian and New red sandstone rocks which stretch from Harborne to the Quinton, though it is much more likely that the boundary between them is a fault. "On the south side of the ridge, at all events, the boundary must certainly be a fault, as near the Stone House brick red sandstone may be seen dipping south at 10°; flattening to 5° at the quarry beyond Weoley Castle.
The northern portion of the coal-field.—The northern portion of the coal-field is the part between the Great Bentley fault and Brereton. None of the faults we have hitherto been examining, with the exception perhaps of the Russell's Hall fault, exercise any marked influence on any large portion of the country. They merely traverse the beds for a certain small distance, and alter their levels over a certain limited space, the amount of the alteration soon diminishing to nothing. If either of these faults did not exist, there would rarely be any material change in the nature or character of the rocks of the locality.
With the Great Bentley fault, however, the case is different.
We have seen that between Wolverhampton and Walsall the Coal-measures crop gradually, but steadily, to the north, so that, first the Thick coal, then the Heathen, then the New mine, rise to the surface of the ground and end towards the north. The Fire-clay and Bottom coals are but a few yards deep about Bentley Lodge and Deepmore Coppice; and it is clear that if this gradual rise of the measures to the north had continued uninterruptedly for a comparatively short distance further, the very base of the Coal-measures would have come up to the surface of the ground, and the Silurian shales and limestones would then have cropped out beyond, spreading north perhaps for many miles. Cannock Chase would in that case have been a Silurian instead of a Coal-measure country.
The great dislocation of the Bentley fault,[17] however, throwing down to the north to the amount of 120 yards (360 feet), brings in the Coal-measures even up to the base of the Thick coal, and that formation then spreads to the north, forming the surface of the ground, till it is concealed under the New red sandstone.
About a quarter of a mile north of the Great Bentley fault another runs parallel to it, throwing down to the south 25 yards, and to that extent forming a trough, or neutralizing the effect of the northern downthrow; still, however, leaving nearly 100 yards of downthrow to benefit the country on the northern side of the trough. (See Fig. 25.) Fig. 25.
Great Bentley Fault.
Scale 6 in. to 1 mile, vertical and horizontal.
1. Old man's coal.
2. Bentley Hey coal.„
3. Heathen coal.„
4. Sulphur coal.„
5. Yard coal.„
6. Bass coal.„
7. Fire-clay coal.
8. Green-rock trap.
9. Bottom coal.
10. Silurian shale, with Dudley and Walsall limestones.
In the trough between these two faults, on the south side of Bentley Heath, they get a nine-foot coal, called the Old Man's coal, which crops out shortly in each direction, as it is never more than 5 or 6 yards deep. The Bentley Hey coal, 5 feet thick, is 50 feet under this; and the Heathen coal, 50 feet under the Bentley Hey. We have already seen that the Old Man's and the Bentley Hey coals mustc, if even only on account of their relation to the Heathen coal, be the bottom beds of the Thick coal separated into two.
The eastern outcrop of the Old Man's coal in the Bentley Trough is just north of the Bentley furnaces, the Bentley Hey coal cropping west of the canal near Birch Hills, and the Heathen and lower coals cropping out successively to the east as we follow the trough towards Ryecroft.
The Great Bentley fault appears to branch towards the east in the manner represented in the map, its branches running up to Rushall and dislocating the measures there, as before mentioned in the description of the Walsall Silurian district. To the northward of the Bentiey Trough, the Bentley Hey coal crops in the bed of the brook (which afterwards forms the little river Tame), north of the Bentley Heath furnaces, and the Heathen coal crops a little to the eastward of that.
These two outcrops run off northward with an undulating line in consequence of slight undulations in the surface and variations in the dip of the beds, for about a mile, the general dip being to the west at an angle of 3° or thereabouts. Several cast and west faults are then met with, the most important of which runs north of the New Invention and south of Bloxwich. This in the centre of its course has a downthrow to the north of 195 feet (65 yards) diminishing, apparently, in each direction. Two little faults, with insignificant downthrows to the south, run between this and Sneyd's Pool reservoir, while one to the south of it running through Herbert's Coppice has a 'downthrow to the south of 45 feet (15 yards) with another very small one to the south of it, having a small downthrow to the north. After being dislocated backwards and forwards by these faults the Bentley Hey coal crops at the south side of Sneyd's Pool, beyond which nothing is known of the outcrop, although the coal itself is met with in the deep sinkings at Essington and Wyrley below the coals worked there, as also in the deeper pits of the Brown Hills district, above all the coals that are usually gotten in that neighbourhood.
The Heathen coal crop is known, after traversing the New Invention fault, in the south-western part of Bloxwich, beyond which it has not been traced, though the coal itself is also said to occur in the deep pits of the Brown Hills district at the proper distance below the Bentley Hey coal.
The outcrops of these coals ought eventually to be discovered along the line of country running by Little Bloxwich, Fishley, and Little Wyrley, or Wyrley Common.
Let us return now to the Bentley and Birch Hills district. It appears that the northern fault of the Bentley Trough likewise splits up towards the east, the branches running off to the east-north-cast, and dislocating the lower Coal-measures and their outcrops in the way represented in the map. Mr. Beckett, of Wolverhampton, is my authority for the three faults running about north-east and south-west from Birch Hills Hall to Harden, and through Goscott Lodge and Coal Pool, which are delineated on the map. The latter appears to be the same as the northern branch of the northern Bentley Trough fault.
It will be recollected that the New mine coal is here already separated into two, known as the Yard and the Bass coal, that the Fire-clay coal changes its name, and further north is called the Cinder coal, but that the Bottom coal continues to carry a thickness of 12 feet, (w hence about Goscott it is sometimes called the 'Thick coal,) up to the southern corner of Pelsall Heath.
This Bottom coal was admirably exposed in October 1858, in a long open work east of Goscott Lodge, belonging to Mr. Brewer. The coal here ran north till it was cut off by 2 fault having a downthrow of some ten yards to the north, which is believed to be the extension of one of the faults already quoted as communicated by Mr. Beckett.
From all the accounts I could collect it appears certain that the faults are even still more numerous in this district than they are represented to be in the map, their complications being in some places so great as not to be unravelled without maps on a much larger scale, and, hardly perhaps even then. The lie and position, then, of the faults and of the broken outcrops of coal about Harden and Guscott, and thence up to Pelsall, which are given in the map, are to be taken as to a certain extent hypothetical. 'They represent the simplest and most consistent and logical explanation that could be arrived at, of a number of isolated facts, which could not be represented at all without some partly hypothetical connexion.
About Pelsall Heath I am indebted to Mr. Gilpin, of Church Bridge, and his ground bailiffs, —- Russell and John Brooks, of Pelsall, for much recent information.
It was from their accounts, confirmed by that of Mr. Brewer and others, that I learnt the precise spot where the Bottom coal begins to separate into two, namely, just at the old public house known as the Red Cow, at the south end of Pelsall Heath.
I must also quote Mr. Gilpin as my authority for the fault running north-east and south-west to the northward of Pelsall Heath, with a small upthrow to the north-west, as shown by the Yard coal just coming in at the corner of Pelsall Heath on the south side of it, while none was found immediately north of it, though it existed under the hamlet marked Pelsall on the map. The Deep coal (or lower part of the Bottom coal) was said to crop in Rail's coppice, and was only three yards deep in a field immediately south of the Ryder's Hayes colliery. As, however, the Deep coal is got in the Ryder's Hayes pit at a depth of forty yards, it is clear there must be a fault with an upthrow to the south of at least twenty yards just south of the Ryder's Hayes colliery.
North of this there are several east and west faults, all having a downthrow to the north, which were pointed out to me by Mr. Gilpin, and also by John Birch, of the Brown Hills. One with a downthrow to the north of twenty yards runs just south of "The Moat," while north of that there is one with a downthrow of three yards in the same direction. Other small faults were spoken of as running parallel to these, and eventually another downthrow of twenty yards to the north, a little south of the canal bridge, now generally known as the High Bridge.
High Bridge Trough.—A little north of the High Bridge there runs, according to the same authorities, a fault about west by north and east by south, having an upthrow to the north of eighteen yards. There is thus produced a trough (which we will call the High Bridge Trough), and in this the Deep coal is worked close to the canal just south of the bridge, at a depth of 100 yards. As we cross these faults from Rail's coppice by Ryder's Hayes to the High Bridge Trough the outcrop of the coals will necessarily be thrown to the east by each downthrow, so that in the High Bridge 'Trough the Yard coal, and perhaps the Bass coal, will alone be able to crop to the surface before the beds are cut off by the Clayhanger and Daw End fault, which runs north and south from the Brown Hills, and will be spoken of hereafter.
North of the High Bridge Trough there are several other east and west faults, as pointed out to me by John Birch of the Brown Hills, having upcasts to the north, and therefore throwing the crops of the coals to the west, until we arrive at a curved fault running from Wyrley Hays by the canal south of Birch's coppice, which has been inserted from the mining plans put at the disposal of the Norton Manor Commissioners, of which we owe the inspection to the kindness of Mr. Beckett. North of this fault the crops of the Yard. Bass. Cinder, and Shallow coals range, apparently unbroken, through Birches coppice to the north till we reach the Rising Sun trough, the Deep coal cropping into or against the Clayhanger and Daw End fault, as formerly described to me by W. Arblaster and confirmed by John Birch. The two little east and west faults near Fishly and the Woodhouse are inserted on John Birch's authority, while those running north-east and south-west between Wyrley Common and Birch's coppice are taken from the mining plans just now alluded to.
Rising Sun Trough.—Approaching Watling Street between "The Rising Sun" and "The Machine" we meet with another twenty-yard trough, as described to me on the ground by John Birch. This will again throw the outcrop of the Yard coal very close to the Clayhanger fault, and thus place the beds in the same relative position as they have in the High Bridge trough. It is in this Rising Sun trough that the deep pit was sunk by Mr. Harrison which passed through the Sulphur. Heathen, and Bentley Hey coals, facts which enable us to connect, with much more assurance than before, the Brown Hillis coals with those of Wyrley.
North of the Rising Sun Trough the faults, with their downthrows, are inserted from the authority of the mining plans used by the Norton Manor Commissioners, and the outcrops of the coals have been drawn in accordance with the indications given by those faults and the fact of the occurrence of the different coals in the different shafts, and their depths from the surface.
The lie and position of the beds hereabouts have already been partly described (pp. 72, 87), as it was necessary to do so in order to arrive at any conclusion as to their structure and constitution. It was shown that however broken and dislocated the beds might be by the different faults that traversed them, they nevertheless preserved all the way from Bentley and the Birch Hills, by Pelsall up to Watling Street, a steady dip to the west of about 3° on an average. North of Watling Street, however, they begin to curve round so as to dip first west-north-west and then north-west, and even north-north-west, at the same low angle of inclination.
Mr. Bills, the ground bailiff of the Cannock Chase colliery, informed me, in October 1858, that they had driven gate-roads in the coals to the north-westward of their present shafts for a distance of 500 yards without meeting with any appearance of a fault or anything that would seem to interrupt their working. The pits then in use were just south of the place, where "Little" of "Little Longfield" is engraved on the map, so that they must have now driven under Norton Bog. He informed me that the beds dipped very slightly towards the north-north-west, being sometimes absolutely horizontal over a considerable space. He confirmed the "lie and position" of the faults drawn in the map about Norton and Norton reservoir. _ I was formerly informed by a collier working at Pelsall that on following the Shallow coal from Pelsall wood towards Fishley it was found to get gradually thinner, and eventually to die out altogether. I was also informed by Jesse Potts, of Wyrley, and others in that neighbourhood, that the Wyrley Eight-foot or Bottom coal cropped a little east of the Bloxwich road about Jacob's Hall.
All the measures of the Wyrley district have a gentle westerly dip, so that the highest beds are only to be found in the most westerly shafts, while they crop out successively towards the east. The most westerly shaft is that of the Waterloo colliery, near Longhouse, where they got, at a depth of 150 feet and a height of 76 feet above the Old Robins coal, a group of beds having 7 feet 4 inches of coal separated by partings of two or three feet, with another little coal 10 feet above them. The beds soon crop out to the east, and are not known in any other of the Wyrley pits. At Essington colliery, however, they get a similar group of beds at a height of 61½ feet above the Old Robins coal, having a total thickness of 7 feet 4 inches of coal with one little parting of 2 inches, and another small coal above them. These two groups of beds are evidently the same, and they are probably the coal which has been found in the wells and in the foundations of the houses at Wyrley bank, just striking the high ground there.
Mr. Gilpin has lately informed me that the whole of the Wyrley district is chopped up by faults of greater or less magnitude, and so numerous that he found it quite impossible to trace them on the one-inch map. The three north-north-east faults, formerly marked on the map, are correct so far as they go, one running through Great Wyrley with a downthrow to the west, and two others running a little east of Wyrley bank with downthrows to the east of twelve and sixteen yards respectively. Of these two the most eastern splits up, towards the south, into several branches, and terminates. The other one, however, continues with an increasing throw towards the south, and turns off towards the east-south-east with a downthrow northwards of thirty-two yards. It may possibly run off in that direction till it is connected with the northern downthrows on the south side of the High Bridge Trough. A little south of Wyrley bank this fault is crossed by another running nearly east and west, with a downthrow to the south of twenty yards. Mr. Gilpin also informed me that among the numerous faults about Church bridge there was always found six or eight yards of red clay in the fault; the fault having that width, and being filled with red clay.
In consequence of these numerous faults it is impossible to lay down upon the maps the outcrops of the coals in any intelligible manner. The dotted lines drawn on the map represent the general approximate boundary of the area within which the respective coals may be found, rather than their actual outcrop. Even where they arc not broken by actual faults they appear as they approach the surface to flatten and undulate, which undulation of the beds, combined with that of the surface, causes each bed to crop in and out several tics successively before its final disappearance.
Added to all these difficulties is that caused by the occurrence of vast quantities of drift, as much as 60 feet of running sand having been sometimes found, as well as clay and boulders. The boulders are many of them granite and often of very large size.
The most southerly of the shafts that can be said to belong to the Wyrley district are two near the Warstone. One of these, situated just about where the "o" of "Warstone" is engraved on the map, has the Wyrley Bottom or Eight-foot coal at a depth of 180 feet (60 yards), while in another pit, about 200 yards to the eastward of it, that coal is only 105 feet (35 yards) deep. The Cannel coal accordingly must crop between these two shafts. At the coal-pits now at work immediately to the cast of the Old Mitre, the Cannel coal was only 10 yards deep. It must, therefore, crop a very little way to the eastward of these shafts.
At Mr. Mills's new colliery to the westward of the Old Mitre (just where the "'T'" of "The" is engraved in the map) the Cannel coal is 396 feet (132 yards) deep, proving, with the gentle dip of the measures, that there must be a fault with a large downthrow to the west, between these two places. The amount of this downthrow is stated at 65 yards (195 feet). The dip of the beds on the downside of this fault is about west-north-west, in which direction they will pass obliquely under the red clays, &e, of Essington Wood. By means of these red clays and the New and Old coal workings on the opposite side of the lane, the fault can be traced by Holly Bank and the Warstone up to Cheslyn Hey, where it probably runs into the western boundary fault.
Its course is about north by east, and there is another little fault parallel to it, some distance east of the Old Mitre, with a downthrow to the west of 15 feet (5 yards).[18]
South of the Essington pits little or nothing is known either of the constitution of the Coal-measures or the "lie and position" of the beds till we reach the greenstone of Wednesfield on the one side, and the Bentley and Bloxwich works on the other.
An old shaft sunk a little east of the New Invention seems to have gone through nothing but Greenstone, of which large blocks may still be found under the soil full of veins of some zeolitic mineral. Other sinkings are reported to have been made formerly to the north of this, between Essington and Pelsall in the district called Essington Wood, and the measures were said to be all destroyed by white rock and green rock trap. White rock trap is to be seen in the cutting of the railway near Landywood, which is the farthest point north at which it is known to exist."
It is also found, as before mentioned, south of Bloxwich about Birch Hills and thence to Pouk Hill, burrowing in the lower measures, and dislocated with them by the various faults that traverse them. If now we go north of the district already described towards Cannock Chase, we meet, first of all, with the old outcrop of coal north of Norton church which has been already spoken of as probably either the Bentley Hey or the Wyrley Eight-foot coal. This coal strikes north-east and south-west, with a dip to the north-west.
Farther north still, is the old outcrop running from near Heathy Hays to Cooper's Lodge, the old pits at Cannock Mill, and the old and present sinkings at Hednesford. At all these places the dip is said to be towards the north-west.
In the old workings on the north-west side of Hednesford Pool a number of step-like faults were said to have been met with, throwing the beds up and down in various directions, but principally down to the west to the amount of a few yards at a time.
From Norton and Hednesford the beds appear to strike regularly north-east towards Beaudesert and Brereton.
The outcrop of a coal may be seen in the valley of the brook south of Castle Hill, while another outcrop may be seen in a little gulley on the north side of it in Beaudesert Old Park. Old coal-pits are scattered all over this old park, all of which were said to go down to the same coal, and none to have been more than about 30 yards deep.
This coal must accordingly lie as nearly as possible in a horizontal position. Beyond it the beds seem to have changed their dip to the south-east.
At the Brereton collieries the general dip of the beds is south-east, at an angle of about 3° to 5°. There are 15 coals, some of which are very thin, in a total section of about 620 feet (see Vertical Section, Sheet 16, No. 1).
On the eastern side of the workings they drove out from the Fifteenth coal, which is there about 460 feet deep, towards the eastward, and came into a hard gravel rock. This was, doubtless, one of the conglomerates of the New red sandstone,[19] and the fault bringing it down to this position was part of the eastern boundary fault of the coal-field. This fault runs just under Mr. Poole's office. South and south-west of this point several shafts have been sunk through some of the beds of the New red sandstone down to the coals. These New red sandstone beds consist of red and white sandstone, and gravels, with some red marls; they appear to be quite horizontal. In the lower grounds they are about 70 or 80 feet thick, but measuring from the top of the inclined plane of the Hayes colliery, belonging to the Marquis of Anglesey, they are nearly 200 feet thick. The coals rise regularly from Brereton Hayes wood, where the Coal-measures are at the surface, at an angle of 3°, so that under the New red sandstone they crop up into the base of that formation. In the pit below the foot of that inclined plane, for instance, they had—
| FT. | IN. | ||||
| 1. | Gravel | 80 | 0 | New red sandstone. | |
| 2. | Red and yellow marl | 6 | 0 | ||
| 3. | Rock | 5 | 0 | ||
| 4. | Clod and batt | 5 | 6 | ||
| 5. | First coal | 4 | 6 | ||
| 6. | Intermediate, with Three coals | 125 | 0 | ||
| 7. | Fifth coal | 4 | 0 | ||
| 230 | 0 | ||||
| FT. | IN. | ||||
| 1. | Gravel | 120 | 0 | New red sandstone, 189 feet. | |
| 2. | White sand rock | 69 | 0 | ||
| 3. | Clod | 110 | 6 | ||
| 4. | Fifth coal | 4 | 0 | ||
| 303 | 6 | ||||
A little beyond the top of the incline is a fault running north-east and south-west, throwing down to the north-west 25 yards.
About ¼ of a mile north-west of this another pit has been sunk, in which they got—
| FT. | IN. | |||
| Gravel | 186 | 0 | New red sandstone, 315 feet. | |
| Ditto and White sand rock | 129 | 0 |
when they came down into the Coal-measures, and were stopped by water; they then bored into a coal just below which was supposed to be the Fifth coal.[20] Farther on, nearly a mile to the north-north-west, in a field of the Birches farm belonging to Lord Lichfield, just south of the Rolling Mill Pool, a boring was made some years ago, the account of which was given me by Mr. George. In this boring they passed down through 418 feet of alternations of "red rock," "gravel," "marl partings," &c. Below that they came into " black marl," and then had alternations of "black marl," "red marl," "white rock," "ironstone," and "red rock," and marls to the total depth from the surface of 612 feet. At a depth of 545 feet they are said to have found a coal 13 inches thick, with a foot of fire-clay below it, and alternations of "red rock," "red marl," and *' blue binds" below that. What these lower rocks were, whether they were true Coal-measures, or whether they were Permian rocks, which, as we have seen, do contain fire-clay and coals, it is exceedingly difficult to say. The mention of ironstone would seem to give it in favour of their being Coal-measures, but there are ferruginous concretions in some of the Permian rocks which in the auger of the boring rods might seem to have been derived from true Coal-measure ironstones.
From the Brereton district, where, as we see, the Coal-measures are partly covered by some beds of the New red sandstone formation, resting unconformably on the edges of the coals, a range of hills runs south-west, ending i in the bold ridge of the Hednesford Hills. All the high 'ground of this range is "composed of beds of soft red and white, sandstone and gravel, which apparently belong to the New red sandstone formation. Along their south-east margin, old coal-pits are abundant, and wherever a little valley cuts into them, the old coal-pits run down it for a short distance. Old coal-pits, with abundance of coal shale on their banks, are found on both sides of the Hednesford Hills, and everything goes to make it probable that at this northern side of the coal-field the boundary is formed by an unconformable overlap of the New red sandstone resting horizontally, or nearly so, on the slightly inclined edges of the Coal-measures. Near Littleworth there are some clay pits, in which blue bricks are made from some beds that appear to be the upper red clays of the Coal-measures, like those at Rumour Hill, at Essington Wood, and at Walsall Wood If this be so, and our identification of these measures be correct, it will follow that all the Essington and Wyrley Coal-measures will there be found below, and probably, therefore, all their coals and ironstones.
The reader will recollect that the southern margin of the coalfield was formed by the Permian rocks resting on the upper Coal-measures in apparent conformity, both being horizontal, or dipping at the same imperceptible angle to the south. Both the north al south boundaries of the coal-field, then, are formed by the simple denudation and removal of the superior rocks, and the consequent appearance of the lower ones at the surface of the ground; the only difference in the two cases being that in the one the superior foals were in apparent conformity to the inferior, while in the other they were distinctly and obviously unconformable.
- ↑ This gives us a dip of 60 yards in 90 = 32°.
- ↑ It is worthy of remark that these faults in the Wren's Nest and the other Silurian elevations do not appear to affect the Coal-measures, although it is clear that these dome-shaped elevations did not take place till after the Coal-measures were deposited. It is plain, therefore, that the cracks and fissures of the dome-shaped elevations are strictly local, or have not much longitudinal extension.
- ↑ As a good illustration of the very careless and ignorant manner in which the South Staffordshire coal-field has been worked. I will describe the way, in which this vertical piece of coal was discovered. A little to the east of it the Thick coal had been worked continuously in a nearly horizontal position at a depth of about 70 or 80 yards, as at A. Fig. 20. The workings were continued towards the Wren's Nest till the coal ended against a fault or supposed fault, or at all events, some "troubled ground." A shaft. B. Fig. 20, was then sunk from the surface, about 30 or 40 yards to the west of this supposed fault, in search of the coal. No notice could have been taken, in sinking this shaft, of the angle at which the beds inclined, and after being continued for more than 70 yards it was abandoned. In fact it must have been sunk the whole distance nearly along the same bed in which it was begun, the beds being nearly vertical, but that was not observed, or not understood, neither were the beds below the Thick coal recognized. The lease of the land was on the point of being given up by the gentlemen who held it, when, a few feet of rubbish being accidentally removed from the surface at a particular spot, the end of the Thick coal was uncovered and of course worked. Even then, however, the ground bailiff, whom I met on the spot, and who had charge of all the mining operations, seemed scarcely to understand that this was merely a piece of the Thick coal bent up into a nearly vertical position, and broken off the horizontal portion below, as shown in diagram. Fig. 20.
Fig. 20.
A. The old shafts.
B. The new shaft sunk in search of the coal.1. Coal-measures.
2. The Thick coal.
3. Silurian shale.
4. The Limestones of the Wren's Nest hill.
These men have a fixed idea that coal grows, that it is still growing and forming in the earth, and that not only the coals and ironstones grow, but that the faults grow likewise; it is not possible, therefore, that they can have any clear ideas of their work, or be able to adapt it to any unusual circumstances.
- ↑ At the Foxyards a ground bailiff informed me that the Thick coal there was not the same as the Thick coal just mentioned, his only reason being that a parting of shale was a foot thicker in one place than in the other; he said there must be a fault between them on that account!
- ↑ Mr. J. Kenyon Blackwell was kind enough to accompany me in tracing the crop of the Thick coal hereabouts, with his ground bailiff, Mr. Waterfield. The outcrop of the coal was perfectly well marked by the occurrence, at the surface of the ground of fragments of "shattery." This is the local name for a well-known indurated shale, streaked red and green, and baked almost into jasper. After extracting the coal, the fragments of coal and shale are piled up in the hollows to afford a partial support to the roof. This mass of fragments is called the "gob," and ia shallow excavations, where the air and water from the surface find ready access, it frequently takes fire, and burns for a very considerable time with a slow combustion. Just at the west entrance of the town of Dudley, in a cutting of the road, smoke and steam may often be seen in damp weather rising through the joints and cracks of a sandstone rock, from the combustion of the "Thick-coal gob" below.
- ↑ Professor Ramsay, however, informs me that subsequent careful examination made by himself led him to the conclusion that the ridge of the Lickey, formed of quartz rock, was everywhere bounded by a fault, as shown in the later editions or the maps. My own notion still is that the appearances may be accounted for by the overlap of the different subdivisions of the Red rocks among themselves, and their total unconformity as a whole to the rocks below.
- ↑ I was informed that in one shaft the Thick coal was actually bent over near the outcrop, so that the same vertical pit passed twice through the Thick coal.
- ↑ Owing to imperfect and apparently erroneous information, a different direction was given in the first edition of the map to the outcrops of the coals at the south end of the Netherton anticlinal, and they were supposed to separate and spread till cut off by a fault. I owe the correction of this mistake to Mr. T. King Harrison of Stourbridge, and his ground bailiff. Mr. John Hatton. The same gentlemen also pointed out to me that the Thick coal of the little basin of the Grange (farther west), although it cropped up towards and into the boundary fault, never actually cropped at the surface, as I had been led to suppose when formerly surveying the ground.
- ↑ By horizontal is here meant "apparent horizontality" only. There may be a slight dip to the southward of 2° or 3°, every geologist knowing that it is impossible to detect such a slight variation from horizontality with anything approaching to certainty or accuracy, except under very favourable circumstances.
- ↑ Mr. B. Gibbons, of Shut End House, described this piece of ground to me from his mining plans.
- ↑ In the original, the table was broken into two columns after row 9, with 178 FT., 6 IN., carried forward from column 1 to column 2. The table is re-combined here, for increased readability. (Wikisource contributor note)
- ↑ It must be borne in mind that all the Silurian shale near these limestones is more or less calcareous, and full of calcareous lumps and nodules.
- ↑ In cutting this canal a number of fine fossils were discovered, especially heads of Eucalyptocrinus and Echinoencrinus, also many fine and rare brachiopods.
- ↑ This was being done for Lord Dartmouth. I did not see the person who advised the sinking, but the man in charge on the bank was not aware that it was the "limestone shale" or "bavin" they were bringing up, although it was crowded with fossils, and bad even nodules of limestone in it; and he told me they were trying then for coal underneath it.
- ↑ It is probable that over this space, even if the Thick coal did exceed that depth, that the Brooch would not come in, as the Flying reed coal or upper part of the 'Thick would come between them.
- ↑ The country here is very much covered by drift. Mr. Yardley, of Tipton Moat, informed me that at Mr. Bagnall's Moorland colliery, near Hateley Heath, it was at one pit 165 feet to the top of the Thick coal, over which there were only 51 feet of "rock binds," &c, for a roof; all the rest, or 114 feet, being drift sand and gravel,
- ↑ Mr. James George, of Bentley, is my authority for all the faults of that neighbourhood, he having placed all mining plans, &c., at my disposal, and frequently communicated to me all the information he possessed.
- ↑ We are indebted to Mr. Beckett for much of the above information, he having gained it from Messrs. Mills, and from Mr. Smallmen, the ground bailiff, of Wednesbury, as also from Mr. Chekley, of Spring Hill, near Bloxwich.
- ↑ Mr. Vernon Poole. Lord Talbot's agent, gave me this and all other information as to the mines under his charge.
- ↑ I was indebted to the late Mr. Figgins for information as to all the collieries under his care.
No farther operations seem to have been carried on at this boring on Flaxley Common, and I think it exceedingly doubtful whether they reached Coal-measures at all. Any such information derived from boring is always of the most uncertain and untrustworthy character.—(Additional note in 1858).
