Page:Quarterly Journal of the Geological Society of London, vol. 35.djvu/851

Rh thin-bedded grits of the Carboniferous. All the beds dip towards the S.S.E. at angles varying from 60°-80°.

6. Not less decisive is the boundary as shown in the fine section of the Coomhola river, which flows into the head of Bantry Bay. This section is described by Professer Jukes in the memoir above quoted. The Coomhola grits, interbedded with grey and black slates with Carboniferous fossils, give place, a few yards north of Coomhola Bridge, to the massive purple grits and slates of the older formation.

Considering that in the Dingle promontory the Glengariff-grit series occupies a position of extreme discordancy to the Old Bed Sandstone, and therefore to the Carboniferous beds above, there is a primâ facie reason for supposing that these formations would be found in a somewhat similar relationship in the region to the south of Dingle Bay. The evidence of this is, however, very small, so much so as to give rise to the impression to which I have already referred, namely, that, as expressed by Prof. Jukes, " from the highest bed of Carboniferous slate as deep down as observation has allowed us to penetrate (into the Glengarift'-grit series), is one great and apparently continuous series of sandstones, or gritstones and clay slates ". It is a common observation how deceptive are such "apparent" conformities, because beds which are widely separated in geological time, if they should happen to be similarly placed as regards the horizon, may easily be considered continuous. Whether, if the two sets of beds forming the Glengariff, Kenmare, and Killarney districts were but slightly inclined to the horizon, a clear unconformity would be observable, I am unable to say ; it is not improbable. But if beds which are only slightly unconformable to each other are both subjected afterwards to tangential forces, causing them to assume a series of sharp flexures, and to rise to the surface at high angles, as is actually the case, it is clear that the original unconformity, whatever it may have been, will have been so completely superseded by the more recent flexuring that it will be obscured and be incapable of observation unless in transverse sections of great depth. It is thus I account for the apparent conformity of the Carboniferous and the Glengariff grits and slates in the regions now under consideration.The flexuring of the strata along approximately east and west axes after the Carboniferous period has been of so intense a nature as to completely overmaster whatever discordant inclinations may have previously subsisted between the two formations. But whether there is a real or only apparent conformity is a question which cannot affect the relation of the beds or the determination of their geological position ; certain I am, in any case, there is not a "continuous series," but, on the contrary, a wide gap in the succession of the beds represented by the absence of the Old Bed Sandstone in this district. I feel satisfied that in this district a whole geological formation — that of the Old Bed Sandstone — which in the adjoining districts