Note 124 — Chapter XXXII · PERMIAN VOLCANOES OF ENGLAND

Only one instance is known where in Staffordshire any igneous rock has been intruded into rocks younger than the Coal-measures (Allport, Quart. Journ. Geol. Soc. vol. xxx. p. 551; Sheet 72 S. W. of the Geological Survey, and Horizontal Sections, Sheet 57). It forms a dyke which has been traced near Norton Bridge, Swinnerton and Butterton, running for 8 miles in a N.N.W. direction, and rising through Permian, Bunter and Keuper strata. It is a highly basic olivine-basalt, and is unquestionably a dyke. Mr. J. Kirkby, who has recently mapped and described it (Trans. North Staffordshire Naturalists' Field-Club, xxviii. (1894), p. 129), suggests that it may be connected with the igneous rocks of the South Staffordshire coal-field. But of this idea there is no evidence. The last point to which the dyke has been traced is some five-and-twenty miles from the nearest known portion of the dolerites of the coal-field. I have little doubt that this dyke is really an outlying member of the great system of Tertiary dykes described in Book VIII. of the present work.