672 ME. F. K. COWPER REED ON THE [NOV. igOO f 



pierced by several veins of fine-grained dolerite of earlier date 

 than the felsite and the accompanying movements (fig. 9, p. 671). 



The irregular intrusive sheets which penetrate the Eaheen Series 

 nearer Raheen are not of a diabasic nature, and belong apparently 

 to a different and probably earlier series of eruptions. A brief 

 description of them is given subsequently. 



Turning now to the neighbourhood of Tram ore, we find one of 

 the principal and most extensive sheets of d i a b a s e in the district 

 exposed more or less continuously in the cliffs on the western side 

 of the bay. It has been intruded for the most part along the 

 junction of the Tramore Limestone and the underlying Tramore 

 Slates, but it frequently crosses the bedding-planes of both. 1 It is,. 

 moreover, later than the movements which have affected their 

 relations and cuts across most of the faults and thrust-planes that 

 traverse them ; but the transverse faults which occur between 

 Tramore village and Great Newtown Head shift the diabase as well 

 as all the other rocks. It preserves the same general petrological 

 characters for its whole course, and fails to produce any marked 

 contact -phenomena in the adjacent rocks. None of the other 

 intrusive rocks pierce it. 



A few yards north of Lady Elizabeth's Cove is the well- 

 known neck which was figured by Du Noyer in the Survey Memoir,* 

 but was described by him as a 'fissured greenstone-dyke.' This neck 

 consists of a dyke-like mass of dark-green coarse tuff, about 

 12 feet in diameter at the base, and running obliquely up the 

 face of the cliff through the diabase, with sharply defined margins. 

 The Tramore Limestones occur on the beach in front, dipping north- 

 westward at 60°. The tuff is entirely composed of fragments of the 

 surrounding diabase embedded in a finer matrix of the same nature. 

 It is thus evident that this pipe was drilled after the intrusion and 

 consolidation of this sheet of diabase. 



A parallel sheet of a slightly different petrological type is seen 

 in the fields adjoining the cliff-road between Lady Elizabeth's and 

 Newtown Coves, and near the top of the fossiliferous series in 

 the latter cove another sheet is exposed. 



On the south side of Oonagappul, and in Chair Cove near 

 Great Newtown Head, a sheet of diabase — probably a con- 

 tinuation of one of those above-mentioned — is found cutting across 

 the felsites, and passing between the ' Metal Man ' and the eastern 

 tower on the headland, to reappear in the cliffs opposite the Stag 

 Rocks, which it probably forms. The southernmost point of the 

 Head is composed of a dark, compact, and fresher-looking dolerite. 



All the foregoing diabases or dolerites are of the nature of sheets 

 following more or less regularly the strike of the beds ; and all the 

 evidence points to the conclusion that they are the latest igneous 

 intrusions along this part of the coast. 



1 See Quart. Journ. Geol. Soc. vol. lv (1899) figs. 2, 3, 5, 6, & 8, pp. 725 et seqq. 



2 Mem. Geol. Surv. Irel. 1865, Explan. Sheets 167, 168, etc. fig. 5, p. 54. 



