On Some Sections in the Lower Palæozoic Rocks of the Craven District

Abstract

The sections to be described are of great interest, as showing an unconformity at the base of the May Hill beds in Prof. Sedgwick’s native district of Craven. The principal section at Austwick has been described by Prof. Hughes, and an unconformity described as existing there, (Geol Mag., Vol. iv, No. 8. ) but an opportunity occurred in the earlier part of this year of more definitely determining the age of the beds just above the unconformity. At Austwick Beck, (Fig. 1.) the Bala beds (1) are seen in a tributary stream, to be unconformably overlain by a coarse conglomerate, (2) as described by Prof. Hughes, interbedded with thin, black, apparently unfossiliferous shales; the whole reaching a thickness of several feet. Above these is a gradual passage, into black shales, (3) which are also seen in the main stream. They are there overlaid by a thin band of hard blue mudstone, a few inches thick, with calcareous nodules, and containing numerous fossils, among which are:— Petraia. Illaenus. Phacops elegans, Bœck and Sars. Leptaena quinquecostata, Mc.Coy. Above these are pale green shales, a few feet in thickness, apparently unfossiliferous. They are surmounted by pale blue flags, (6) containing Monograptus priodon and Monograptus vomerinus, and these by the Austwick grits (7) above which are various alternations of grits and flags. At Crummack Beck Head, near the last described section, the Bala beds are seen overlain by a similar conglomerate, again with an unconformable junction. Both this conglomerate and that at Austwick Beck consist ...