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ON THE GEOLOGY OF THE NORTHERN PART OF THE COUNTY OF STAFFORD.
BY J. B. JUKES, B.A. F.G.S.
THE geological structure of the northern part of the county of Stafford is so intimately connected with that of Derbyshire that, although my materials are very scanty, it appears better to throw them together in the form of a supplement to my last paper, than to break the connection between the two. The rocks which enter into the composition of N. Staffordshire are precisely the same with those of Derbyshire, with the exception that no toadstone, or other igneous rock, is any where visible. The diluvium also differs somewhat, since there is in Staffordshire a greater abundance of fartravelled boulders than in Derbyshire; large blocks of porphyry, granite, and other rocks, washed from the mountains of Cumberland, may be seen scattered over the Pottery coal-field and the country to the south, forming part of the great northern drift which has swept a mass of ruins over all the country intermediate between Cumberland and Worcestershire, and some of which have even been carried as far as the Bristol Channel.
In passing from Derbyshire into Staffordshire, little or no change takes place in the character of the scenery. The same high brown or purple moors of gritstone, the same green hills of limestone, and the same richly-wooded tracts of new red sandstone, may be seen in one as in the other county. There is, however, by no means that regularity of structure in N. Staffordshire, considered as a whole, which was observable in Derbyshire. The mountain limestone is confined to a patch on the eastern side of the district, while the distribution of the shale and gritstone, the coal measures and new red sandstone, over the remainder is, at first sight, very irregular. This distribution will be best understood by marking on a map first, the outline of the mountain limestone, and next, of those parts occupied by coal measures, the intermediate portions being understood to
Since writing the first part of the Geology of Derbyshire, I have been informed by Mr. Barker, of Bakewell, of the occurrence of granite boulders in Haddon field, and by Prof. Sedgwick of his having observed them on the summits of the hills bordering Derbyshire and Cheshire.
+ Of course, its appearance on the surface is here meant, as it is believed to underlie all the rest of the district.
VOL. IX., NO. XXVI.
be composed of gritstone or shale, except when any of these rocks may be concealed by the overlying beds of the new red sandstone.
Beginning, then, at Berrisford Hall, near Hartington, the boundary of the mountain limestone runs by Narrowdale to Gateham, whence it sweeps round to the north, along the flank of Ecton hill, up to Warslow. From Warslow it runs with an undulating line to the west, to a point about one mile beyond Upper Elkstone, whence it deflects to the S. running nearly in a straight line S.E. as far as Waterfall and Waterhouses. From this point it sweeps round the bold hill of Caldon Low and along the S.W. flank of the Weaver Hills to Ramsor, whence it turns to the N.W. and enters Derbyshire again near Thorpe, at the extremity of Dove Dale.
The principal coal-measure district is that called the Pottery coal-field. This has a triangular form, the apex of which is at Biddulph, the eastern side running thence in a nearly straight line to the eastern corner of the town of Lane End; while the western, after sweeping round the southern extremity of Mole Cop, and enclosing Talk-o'-the-Hill, passes through Audley to the neighbourhood of Madeley manor house. The base runs from Madeley manor house, S. of Newcastle, to the S.E. corner of Lane End aforesaid. A much smaller district, which may be called the Kingsley or Cheadle coal-field, has a somewhat similar shape, the apex of which is at Ipstones, the eastern side passing by Froghall to near Oakamoor, the western running to the west of Dilhorne, and the base being an irregular line passing from the neighbourhood of Dilhorne, by Delph Houses, to the S. of Cheadle, and thence by Hales Hall to the Churnet, just N. of Oakamoor. In the northern corner of the county are several small tracts, where coal is worked, either on the back of the gritstone hills, or in the hollows made by the depression of their beds. Of the latter a remarkable instance occurs about half way between Leek and Buxton, about Goldsitch, where is a small patch of coal measures about 14m. long by m. broad.
It remains now to notice the distribution of the new red sandstone. Beginning at Ashbourne, this rock will be found running up the valley of the Dove in a narrow tongue, forming the middle of the valley and also the sides, up to a certain height, as far to the N. as within a mile of Thorpe. Having crossed the valley of the Dove, the boundary of the new red sandstone is found to run towards the S. at the back of Church Mayfield, but shortly to turn N. again, and run in the same manner up the little valley that comes down by Stanton, that it does up the valley of the Dove. From the bottom of this valley the boundary is more regular, running N.
of Ellastone and Wootton Hall, by Farley, to Oakamoor. From Oakamoor the line mentioned before as running S. of Cheadle to a point about one mile west of Dilhorne, is the common boundary of the new red sandstone and the coal-field. From this point the new red sandstone runs up to Cellar Head, and thence by Holme down to Park Hall, near Lane End. The boundary of the Pottery coalfield then becomes that of the new red sandstone along the line by Madeley, Audley, and north of Talk-o'-the-Hill, to the S.W. end of Mole Cop, when the two formations separate again, and the new red sandstone runs into Cheshire, lying at the foot of the range formed by Mole Cop, Congleton Edge, and Cloud Hill. All the northern division of the county S. of the line now traced as running from Ashbourne, by Cheadle and Newcastle, to Madeley, is formed of the new red sandstone, without the appearance (so far as I am aware) of any other rock. To the north of this line all the country not previously included within the boundaries of the mountain limestone and the coal districts, is formed of gritstone and shale. A belt of shale, as usual, surrounds the mountain limestone, and a ridge of gritstone forms the boundary of the coal districts; but the two formations pass too insensibly one into the other to admit of drawing lines of demarcation, except on a map of very large scale, and after much greater time and labour than I have bestowed on them. Within the district thus occupied, however, there is yet to be noticed a very remarkable outlier of new red sandstone. From a hamlet called Fould, about two miles N. of Leek, down to the borders of the Cheadle coal-field about Consal, the valley of the Churnet is composed of this rock, which, as in the valley of the Dove above Ashbourne, forms the bed of the brook, and rests against the neighbouring hills up to a certain height, occasionally perhaps two hundred feet above the level of the river.* The same thing takes place, too, in a lateral valley that comes in from the W. below Cheddleton; new red sandstone is found up it as far at least as the village of Endon, which stands on an eminence composed of that rock. Another outlier of new red sandstone, but smaller and nearer the main mass of the formation, is that covering part of the Cheadle coal-field, and on which the town of Cheadle itself stands. The structure of the districts thus mapped out, and the position of the beds of which they are composed, is well worthy of a more accurate examination and description than they have yet received. All I can do, however, is, to give a few hints respecting them.
The town of Leek itself stands upon new red sandstone.
The mountain limestone is, no doubt, much broken by faults, some of which are very conspicuous and apparently of great magnitude; but, nevertheless, one of two things must be the case, either there exists no toadstone whatever, and the Staffordshire limestone is one undivided mass, or else there are no faults of sufficient magnitude to bring it up to the surface. It is, perhaps, more likely that the former should be the case than the latter. Another circumstance strikes us very forcibly in Staffordshire, and that is, the greater abundance of extraordinary contortions in the beds of limestone than is generally visible in Derbyshire. Whether this circumstance be an evidence of greater disturbing force, however, or of a modified exhibition of it, I am not prepared to say. Along the whole of that most lovely valley of the Manifold, from Warslow to its junction with the Dove below Islam Hall, these contortions are continually exhibited, but most especially where the river cuts through the north end of Ecton hill, a continued succession of saddles and curves being there shewn, which make it appear that the whole district is puckered, as it were, into small ridges and furrows running generally north and south, but having others crossing them at various angles.-(See diagram). It is probably to this continually arched position of the beds that the singular phenomenon is due of the sudden engulphing of a brook and its re-appearance after a few miles, which takes place in two or three instances in this district. The great richness in mineral products, too, of Ecton hill, and some other spots, may possibly be partly dependent on the fractured state of the rocks. It is remarkable, however, that copper, which is almost unknown in Derbyshire, should be the most abundant metal in many of the mines of N. Staffordshire.
The quarries at Waterhouses, half way between Leek and Ashbourne, is another place where the broken and disjointed and variously-arched position of the limestone beds may be well seen; and indeed hardly any considerable quarry or face of rock can be visited without seeing some curve or contortion exposed. Throughout all this disturbance, however, the action of some general law regulating the direction of the forces, can be traced in the fact that an inclination of the beds towards the N. or S. is very rare, almost every dip being E. or W. or within at most 45° of those points.
The large tract composed of the shale and gritstone has been affected in the same way as the limestone district, many changes of dip, and frequent steep inclinations of the beds, being constantly met with, and many great faults, no doubt, existing, whose situation is not so obvious The direction of these inclinations corresponds
with those before mentioned, and a careful examination would no doubt detect numerous anticlinal and synclinal lines running across the country, with an approximately N. and S. direction. An anticlinal line, running N. and S. by Wetley Rocks and Cellar Head, certainly separates the Cheadle coal-field from that of the Potteries for some distance, as by Cellar Head shale may be seen, containing a bastard limestone, at the top of the hill, the gritstone dipping rapidly from it on either hand. How far, however, this line may run to the S. is unknown, on account of the overlying beds of the new red sandstone concealing the carboniferous rocks from our inspection. On the other hand, the position of synclinal lines in this direction, or lines towards which the rocks bend downwards, is marked by the position of the coal-fields themselves, which of course lie in troughs formed by the bending downwards of the gritstone rocks on which they rest. The small patch of coal measures mentioned before as occurring at Goldsitch, lies in a deep hollow of the gritstone rocks, which rise rapidly from under it on every side into lofty hills, more especially to the W. and S. on which sides the summits of the hills exhibit great beds and ledges of rock, whose rapid dip towards the valley may be seen a mile or two off. The coal measures themselves, of course, follow the position of the rocks on which they rest, and, being horizontal in the centre of the basin, crop out on every an angle of 30°, except towards the N. where they are cut off by a fault. One bed of coal is here worked, which for a short distance is five or six feet thick: there are two others, neither of which exceed two feet. The northern part of the Cheadle coal-field, about Kingsley, contains three beds of coal, the thickest of which is three feet; the beds are very nearly horizontal, what slight inclination there is being towards the N.W. S. of Cheadle, however, and about Delph Houses, five beds of coal are worked, the uppermost of which is six feet thick, the whole section having a thickness of one hundred and six yards, and over this part the inclination is S.W. the beds dipping at the rate of one in nine. At Dilhorne, I believe, similar beds are worked, but they here crop both to the N. and W. shewing that the anticlinal line mentioned before as passing by Cellar Head, throws out the beds on this side, and thus far, at least, produces a real separation between the Cheadle and Pottery coalfields.
Concerning that far more extensive district, the Pottery coalfield, I regret that all the information I was able to procure is exceedingly scanty, owing partly to my own want of time, and partly to an absurd jealousy which still lurks in that district, with respect