Page:Quarterly Journal of the Geological Society of London, vol. 35.djvu/847

Rh the Old Red Sandstone in the Kenmare and Glengariff districts. In the Dingle promontory, as has been stated, the Old Red Sandstone is in the highest degree unconformable to the Silurian and "Dingle beds;" but it has been supposed that in the districts south of Dingle Bay, there is a gradual passage from "the Dingle beds" (Glengariff-grit series) up into the Old Red Sandstone and Carboniferous series. On this account it was found impossible to draw a boundary between the Old Red Sandstone and Glengariff-grit series, and the whole is coloured "Old Red Sandstone" on the Survey maps. Again, in the words of Griffith, the matter is thus stated:—"Here, at the very threshold, we are apparently met with an insurmountable difficulty, and that is, that we actually find the Glengariff grits gradually conforming upwards, not only into the Old Red Sandstone . . . . . but also, as a matter of course, conforming to the plant-beds of the Yellow Sandstone, such as those of the Coomhola or Roughty rivers, as well as to the Carboniferous slate, the Lower and Upper Limestone, and the Coal ". Certainly, if this "apparently" conformable passage was a reality, it would present a very strange and unusual phenomenon in geological science; for it would amount to this, that within the short distance across Dingle Bay we should have two formations, on one side in the highest degree discordant to one another, and on the other, concordant, and passing insensibly the one into the other. On the first consideration, therefore, the supposition is very improbable, because it may well be questioned if such an amount of disturbance and denudation as took place between the formation of the "Dingle beds" and the Old Red Sandstone could be confined to the narrow space of the Dingle promontory. As a matter of fact, however, I believe the supposition is entirely groundless, and arises from the resemblance which exists between the upper part of the Old Red Sandstone and the upper beds of the "Dingle" or "Glengariff-grit" series.

For the purpose of investigating this question, my colleagues and I visited the sections on both sides of the Roughty river at Kenmare, also at Sneem, which lies about twelve miles west of Kenmare, on the northern shores of Kenmare Bay, and lastly at Glengariff; and we ultimately arrived at the conclusion that at all these points the Lower Carboniferous beds rest directly upon the "Glengariff" or "Dingle beds," the Old Bed Sandstone being altogether absent. If this be so, there can be no such passage as that supposed; on the contrary, there is a wide hiatus, a whole formation being absent at the line of junction. I shall now give a brief account of each of these sections, beginning with those in the neighbourhood of Kenmare.

1. Kenmare Sections.—The first is one near Roughty Bridge, about three miles above the village of Kenmare, and on the south bank of the Roughty river. It is of special interest, as it commences in the Carboniferous Limestone, which lies in a narrow trough. The beds dip at high angles, 70°–80°.

The upper portions of the beds underlying the Carboniferous slates