Vol. 56.] 



IGNEOUS EOCKS OF COUNTY WATEKFORD. 



671 



vents in East Fifeshire, described by Sir Archibald Geikie. 1 That it 

 was formed after the beds which it pierces had received their cleavage 

 is shown by the identical character of the cleaved fragments in the 

 pipe with that of the surrounding solid rocks. 



c. The Basic Sills and Vents. 



The basic and intermediate rocks of the coast occur prin- 

 cipally in the form of large intrusive sheets of diabase, dolerite, or 

 allied rocks, and are sometimes associated with necks composed of 

 similar materials in a clastic condition. These pipes of ' green- 

 stone '-agglomerate represent in some cases the vents from which 

 the flows occurred. There is, however, no evidence that any of 

 these flows took place at the surface, and they all seem to have 

 been forced into or between the older rocks, sometimes along the 

 bedding-planes. 



In addition to several large and conspicuous sheets, many 

 smaller tongues and veins of similar or allied rocks are exposed, 

 all of them of late date, but they do not universally belong to the 

 same period of intrusion. 



At Newtown Head, Passage, the mass of felsite (fig. l,p. 659) is 

 distinctly seen to have burst through the diabase and other rocks of 

 the headland, as described on p. 658. The diabase, which first 

 appears at a small spur, down which a path leads to the beach, has 

 broken through the 



older bedded series Fig. 9. — Section at Newtown Head, showing 

 (Raheen Series) of the relations of the intrusive rocks. 



felsites and tuffs, and 

 encloses some large 

 blocks of them. It 

 forms a large irre- 

 gular exposure on 

 the foreshore and at 

 the base of the cliffs, 

 and its margin where 

 it is in contact with 

 the later outburst of 

 felsite is much shat- 

 tered, crushed, and 

 decomposed. 



A considerable 

 amount of distur- 

 bance has taken place 

 in the mass of the 

 diabase subsequent 

 to its consolidation, 

 but prior to the fel- 

 sitic eruption. The diabase itself varies slightly in texture, and is 



A = Dark greenish-grey felsite. 

 B = Crush-zone of D. 

 C = Intrusive tongues of dolerite. 

 D = Dark-green coarse diabase. 

 D'= Crushed diabase. 



E = Included mass of pale-grey trachy tic andesite. 

 F = Patch of breccia, consisting chiefly of frag- 

 ments of E and a grey felsite. 



Ancient Volcanoes of Great Britain' vol. ii (1897) pp. 73 et seqq. 



