On the Igneous Rocks occurring between St. David's Head and Strumble Head (Pembrokeshire)

Abstract

I. I ntroduction . T he area with which this paper deals adjoins the strip of coast lying between St. David's Head and Strumble Head in Pembrokeshire. No detailed account appears to have been given hitherto of the igneous rocks of the greater part of this district, but the Strumble-Head rocks have been described by Mr. F. R. Cowper Reed in his paper on the geology of the Fishguard District. Adjoining parts of the county have also received attention: Mr. John Parkinson has discussed the Prescelly area, and the district south of St. David's, including Skomer Island, has been described by various writers in considerable detail. The granitic rock of St. David's, of classic interest by reason of its disputed igneous origin, has been the subject of exhaustive discussion by Henry Hicks, and has been described petrographically by Thomas Davies, E. B. Tawney, Prof. Bonney, Sir Archibald Geikie, the Rev. J. F. Blake, and Prof. C. Lloyd Morgan. Murchison made some reference to the trap-rocks of Pembrokeshire in his well-known memoir, and these rocks were mapped on the 1-inch scale by the Geological Survey in 1845, under the superintendence of Sir Henry de la Beche, the igneous rocks being re-surveyed in 1855-56 by W. T. Aveline. Of the stratigraphy of this portion of Pembrokeshire there is still much to learn. Hicks mapped the outcrops between St. David's and Abereiddy Bay, and Mr. Cowper Reed has done the same for the neighbourhood of Fishguard. These lines are approximately shown in the accompanying sketch-map (P1.