The South Staffordshire Coalfield/The Drift...
The Drift or Superficial Accumulations.
I have reserved to this place the little I have to say on this subject. This little consists of a few fragmentary notices rather than any connected account.
Blocks of granite and old trappean rocks, evidently belonging to the Great Northern drift, are found in great abundance all along the western boundary of the coal-field, especially about Bushbury, and thence towards Cannock. 'They occur abundantly also over all the New red sandstone country on the west of the coal-field. They may be found occasionally, but by no means abundantly, within the limits of the coal-field itself, but on its eastern side they are, as far as my recollection serves me, comparatively very rare. They are seldom found embedded in any great mass of drift matter, but lie for the most part loosely scattered over the surface of the country.
There is another set of drifted materials which I should be inclined to separate from the Great Northern drift, because large granite blocks are rarely, if ever, found in it, while it often abounds in F chalk flints, and sometimes in broken fossils of the Lias and Oolitic formations, and seems, therefore, rather to be derived from the east than the north. This occurs in the shape of sand and gravel lying in patches here and there about the district, or sometimes as a red c Red clay, containing water-worn Lias fossils, is frequently found about Wolverhampton, or between that town and Shiffnal, on the cutting of the Shrewsbury railway, resting on the New red sandstone. A block of galena, also, as big as a man's head, was once procured from it near Wolverhampton. It never has been found, so far as I am aware, to contain any fragments of arctic shells, or of any other shells or fossils than those before mentioned as drifted out of other formations.
There is yet another class of drift, apparently distinct from both the above, as never containing any granite or northern boulders, nor any water-worn fossils or recognizable fragments of other formations. It consists, for the most part, of very fine red sand, with a few occasional lines or thin beds of very small well-rounded pebbles, principally of quartz or quartz rock. This occurs in immense quantity about West Bromwich and Hill top, in places between Darlaston and Walsall, and thence towards Willenhall and Pelsall. Large and deep excavations in it may be seen at Moxley Sand hole,[1] between Wednesbury and Bilston, whence it runs in a pretty well defined band, about a quarter of a mile wide, up to Marshend, a little east of Wednesfield. It makes no feature at the surface of the ground, but comes in suddenly 50, 60, or 100 feet deep, filling up a pre-existing valley in the Coal-measures, and causing great trouble to those who have to sink through it to the beds below. North-east of Wednesbury the New mine coal suddenly crops into this loose sand at a depth of 90 feet below the surface of the ground.
This loose red sand seems to be the washing of the adjacent New red sandstone, and when it is a little consolidated, which it sometimes is, and only a small section of it is exposed, it is extremely difficult to distinguish it from undisturbed New red. This is especially the case about Pelsall and Pelsall Heath. I should class with this drift, in time and manner of accummulation, those quartzose gravel beds which do not belong to the New red sandstone, but which are derived from the washing of its 'pebble beds" or conglomerates. These occur very abundantly in some places; they were well shown formerly in the deep cutting of the canal at Smethwick. They spread over all the southern part of Cannock Chase, resting on the Coal-measures there, having been brought probably from the undisturbed pebble beds or conglomerates of the New red, which form the northern portion of the Chase.
Whether these three sorts of drift all belong to one and the same period, that commonly known by the name of the glacial period, is a problem yet to be solved. I may be pardoned, perhaps, for saying that I think many geologists are too hasty in speaking of all superficial drifted materials as "the drift," as if there could only be one drift. We have already seen that there was both a Permian and a New red sandstone drift, portions of which, when they appear isolated at the surface, would be taken by any one for parts of the " glacial drift," at first sight.
I know of no reason, for instance, why the drift clay, and sand and gravel containing Chalk flints and Lias fossils, might not be of the age of the gravels of the Plastic clay, though I am not at all disposed to assert that they are so, because, as I know of no evidence against such supposition, neither do I know of any reason for it.
If it be true that stags' antlers were found under the red sand at Moxley, it would, of course, be a proof of its comparatively recent origin; but in the absence of that or some such proof. I should hold myself prepared to find that these sand and gravel washings of the New red sandstone were of any age from that of the Oolites down to the Pleistocene.
- ↑ Some men working in these sand holes assured me that a stag's antlers had once been found in this drift at a depth of 40 or 50 feet below the surface.