II.—Second Note on the Pebbles in the Bunter Beds of Staffordshire

Abstract

In my brief paper published in this Magazine for 1880 (Decade II. Vol. VII. p. 404), I mentioned that pebbles of felstone were not uncommon in the Bunter conglomerate on the northern part of Cannock Chase. Since that time, as opportunity has occurred, I have been making a more special study of these pebbles, and think it may be worth while publishing a description of some of the commoner varieties, as a contribution to the lithology of this interesting deposit and a help to the determination of the question of the origin of its material. I believe that I have observed most of the varieties, which commonly occur in the district, but do not pretend (for circumstances have not allowed of this) to have made anything like a complete collection. Many of my specimens have been derived from the broken materials spread upon some roads newly made over the portion of the Chase in the vicinity of Rugeley, but several of them were obtained in a large pit in the Bunter itself, by the side of the railway on the road to Hednesford, and I was able by a careful search in it to identify most of the varieties that I had collected elsewhere. I cannot say that erratics are absolutely unknown in this district, but they are extremely rare, and there is practically no danger of making a mistake as to the source of the pebbles. These pebbles of felstone (to use an inclusive term) appear to be by no means rare. I think one could hardly search a couple of square yards of a newly “metalled” road without picking up a fragment. Now and then specimens are found with a dark ground-mass, and occasionally one which seems to be an indurated felspathic breccia; but in the majority there is a certain common character, though there are many varietal differences. These have a compact ground-mass, varying from a pale brick-red (the commonest) to some tint of pinkish-grey.