least, one important value—that they will strictly define the limits of the coal-bearing tracts.
I propose in this paper to show to what extent the British Carboniferous rocks have their representatives in Ireland; after which I will endeavour to point out the significance, as bearing on the question of classification, of that remarkable series of beds already referred to, known as the "Gannister Beds" of the late Professor Phillips; and lastly I shall state the conclusions which seem to me to arise from the above considerations, and which seem to render desirable a fresh mode of classifying the Carboniferous beds, with a view to the introduction of a "Middle Carboniferous series" to include all the strata lying between the Mountain Limestone and the Middle Coal-measures, and including the Yoredale Beds, Millstone Grit, and Gannister Beds.
Arrangement of the Subject.—In considering the subject of the Carboniferous beds of Ireland, it will be desirable to divide it into three portions, taking:—I. The Southern Coal-districts; II. The Northern Coal-districts; and III. The Ballycastle Coal-district in Co. Antrim, which differs from both. But before doing so it will be desirable, for the sake of comparison, to state the succession of the strata in the British Carboniferous districts, as now very generally recognized[1]; and for the purpose of easy reference I have arranged them into stages.
The British Carboniferous Series.
| Name of Formation. | Localities. | ||
Essentially Freshwater and
Estuarine Beds. |
Stage G. Upper Coal-measures.—Reddish and
grey sandstones, breccias, and clays, with thin coal-seams and limestones. |
Manchester, Stoke-on-
Trent, Newcastle- under-Lyne, S. part of Dudley Coal-field; Banks of the Dee near Ruabon; Hamilton and Ayrshire in Scotland. | |
Fossils (freshwater or estuarine).—Fish
(migratory); Crustacea, Cythere inflata; Annelids, Spirorbis carbonarius. | |||
Stage F. Middle Coal-measures.—Yellowish
sandstones, clays, and shales, with thick coals. |
Central portions of all
the coal-fields of England and Wales; Upper Coal-measures of Scotland. | ||
Fossils (freshwater or estuarine)[2].—Fish
(migratory); Molluscs, Anthracosia, Anthracomya; Crustacea, Beyrichia, Estheria; Annelids, Spirorbis. Marine species, rare. |
- ↑ 'Coal-fields of Great Britain,' 3rd edit. p. 80. Index-sheet of formations of the Geological Survey (1871).
- ↑ Though the fossils of the Middle Coal-measures consist of those bivalves above named, and of whose habitat there is some doubt, true marine bands are occasionally found, as at Ashton-under-Lyne, with Discites, Aviculopecten, &c. See "Geology of the Country around Oldham," Mem. Geol. Survey, p. 64.
