158 MB. E. E. C0WPER EEED ON THE GEOLOGY OF [May 1 895, 



activity, if it be correct to assign the beds of Strumble Head to the 

 Upper Llandeilo and Bala. 



Unfortunately the slates there afford no fossil-evidence to settle 

 the point ; but, for the following stratigraphical reasons, the con- 

 clusion as to their age seems very probably correct : — 



(i) The occurrence of definite Lower Llandeilo lavas, with under- 

 lying and overlying sedimentary rocks containing well- 

 marked fossils, on the east side of Goodwick Bay. 



(ii) The agreement in strike of both sets of beds. 



(iii) The probability of the occupation of the intervening area of 

 Goodwick Bay by Middle Llandeilo beds. 



(iv) The soft, black, argillaceous shales of Feidr Pont Eglwys, 

 near Pont Iago and Llanwnda, which break up into small 

 splintery fragments, may very well correspond to the grap- 

 tolitic shales of Newport and the lithologically similar beds 

 of Abereiddy Bay. 



(v) The agreement in position of the volcanic series and black 

 shales with what we should expect from the effects of the 

 Pwll Ceunant and Goodwick faults. 



In the unfortunate absence of fossils from the slates and flags of 

 Strumble Head there must at present remain a doubt as to their 

 age ; but the balance of evidence is in favour of the view that the 

 Goodwick lavas and breccias are on the horizon of the great volcanic 

 belt between Coch y Ceiliog (Pwll Ceunant) and Newport, and that 

 the other volcanic rocks on Strumble Head are higher in the Bala 



(b) The Contemporaneous Volcanic Rocks. 



(1) General Characters and Distribution. 



The age of the rocks has been already discussed, but a brief re- 

 capitulation of the conclusions arrived at will be useful. Firstly, 

 the volcanic series that extends from Manorowen Hill through Cwm 

 Bach, Bigney, across Fishguard Harbour to Castle Point is Lower 

 Llandeilo. Secondly, the great volcanic belt that runs eastward 

 from Coch y Ceiliog (by Pwll Ceunant) through Cam Fran, Bwlch 

 Mawr, and Cam Ffoi to the Clydach valley belongs to the base of 

 the Upper Llandeilo ; and to this same horizon belongs the belt 

 stretching inland in a south-westerly direction from the north- 

 eastern extremity of Strumble Head past Goodwick and through 

 Cam Gelli. Thirdly, the central outcrop of lavas and breccias 

 north of the Garn Fawr-T Garn intrusion is probably of Bala age, 

 and is on a higher horizon than the Goodwick lavas. This central 

 volcanic group of beds is cut obliquely to its strike by the Garn 

 Fawr-Y Garn intrusion, but may be recognized also on the southern 

 side of the diabase near Pwll Deri, where it has thinned out and 

 split up into separate thin lava-flows and tuff-beds with interbedded 

 slates, flags, and sandstones. The tendency of these three sets of 



