The Greenstone Ridge at Ty'n-y-coed, Radnorshire

Abstract

In an earlier paper (8)an olivine-basalt was described from this locality; the present contribution may be looked upon as a continuation of the study then begun. This basalt is best exposed at the southern end of the ridge in a small quarry, but several exposures are to be seen farther north. All these, where the compact, fresh-looking basalt is to be observed, are situated along or near the eastern margin of the ridge, a fact particularly well shown near the northern end. On the western side of this strip are several exposures of fine-grained, brownish rock, so well jointed that it is almost impossible to get a good specimen; an additional feature of importance is that the exposed surfaces are frequently striated. That these striations are not of glacial origin is demonstrated by their occurrence on newly-quarried surfaces, and also by the fact that specimens bounded on two sides by these striated surfaces may be collected.