Vol. 67.] 



SKOMER VOLCANIC SERIES. 



181 



Jeffry's Haven shows Upper Llandovery shales resting upon 

 quartzites and shales, and followed downwards by the basic lava 

 which here takes on a good pillow-structure. Below the lava are 

 more quartzites about 50 feet in thickness, which rest directly upon 

 typical sedimenrs and volcanic rocks of the Skomer Series. Although 

 there are some signs of movement between the Skomer Series and 

 the overlying Llandovery rocks, it seems unlikely that any beds 

 have been removed from the sequence. 



Taking the Llandovery volcanic horizon as a datum (see fig. 2), 



Fig. 2. 



No. I. 

 Anvil Bav. 



Upper Llandovery 

 Shales 



Conglomerate 



No. II. 

 Jkffry's Haven. 



I Upper Llandoverv 



S Shales. 



(. Quartzite. 



Quartzite and shales 

 with Lingtda, 



00000 



o o o o 

 00000 

 o o o o o 



I Pillow-lava. 



f Quartzite and con] 

 C glomerate. 



| Basalt of Skomer 

 I Series. 



[Vertical scale : 

 1 centimetre =50 feet ; 

 or 1 inch =125 feet] 



Red clay 



Dolerite of Skomer 

 Series 



and comparing the thickness of Llandovery sediments represented 

 below it in the two sections, we at once notice a great disparity ; 

 for, whereas there are at least 250 feet of beds between it and the 

 Skomer Series in the Eenney Slip and Anvil Bay section, there are, 

 at the most, only 50 feet of beds in the Jeffry's and Mouse's Haven 

 section. This would point to an overlap within the Upper Llan- 

 dovery and an overstep of the Upper Llandovery on to the Skomer 

 Series. Therefore, despite apparent concordance in dip and strike, 

 I am inclined to the conclusion that the Upper Llandovery 

 rests unconformably upon the Skomer Series, and that 

 the volcanic rocks are thus of pre-Upper Llandovery 

 age. 



