304 STKATIGRAPHICAL GEOLOGY 



The Flagstone Group is the equivalent of the Millstone Grit of 

 Bristol and South Wales, and the true Lower Coal-measures are the 

 beds which overlie these flagstones, many of the same marine shells 

 occurring in them as in the Gannister Beds of Northern England. 4 

 The Jarrow collieries in Queen's County are known for the 

 number of Amphibian remains which have been obtained from them. 

 Northern Counties. The most important tract in the north 

 is the Tyrone coalfield, which lies to the north of Dungannon and 

 contains many good seams of bituminous coal. The succession as 

 given by Mr. Hardman 5 is as follows : 



Feet. 

 Middle Coal-measures. Soft sandstones and shales with 



coals, fireclays, and ironstones 930 



Lower Coal-measitrcs.- Hard sandstones and shales with a 



few thin coals and ironstones 1000 



Millstone Grit. Coarse grits and sandstones . . . 60 to 200 



About 2000 



Upper Carboniferous rocks occupy a considerable area in the 

 counties of Leitrim and Fermanagh, and their sequence is the same 

 as in Tyrone, but only part of the Lower Coal-measures come in 

 above the Millstone Grit. 



5. South Wales and Bristol Area 



This area exhibits a different development of the Westphalian 

 Series from that found in other parts of the British Isles, and it is 

 not yet certain how far the natural divisions of the series in this 

 southern area can be compared and correlated with those of more 

 northern districts. Moreover, the succession found in the great 

 coalfield of South Wales is not the same as that occurring in 

 Bristol and Somerset, and the differences between the two areas may 

 be tabulated as follows : 



South Wales. 

 Upper Coal Series ( = Upper C.M.). 



Pennant Grit Series ( = Transition 



C.M.). 

 Lower Coal Series ( Middle C.M.). 



"Millstone Grit Series" (of doubt- 

 ful age/. 



Bristol and Somerset. 



C.M. 



\ Upper 



Trans. C.M. 



Radstock Beds 

 Farrington Beds 

 Pennant Grits " 

 Vobster Group 

 (Not represented.) 



"Millstone Grit" (partly of 

 Avonian age) 



In the Bristol coalfield the Avonian limestones pass up through 

 shales into the Millstone Grit, the lower part of which probably 

 represents the Yoredale Beds of northern areas (see p. 253). As to 

 the age of the higher part there is no evidence, but there seems to 



