TIIK CARBONIFEROUS SYSTEM 



measured from the Woreley 4-foot coal to the flags below the 

 Arlrv mine coal, the thickness is about 3500 feet In York- 

 shire and Nottingham these measures are from 2000 to 3000 feet 

 thick, and are so entirely like those of Lancashire that several 

 of the Yorkshire coal-seams can be identified with their counter- 

 parts on the west ; thus the " Silkstone " of Yorkshire is the " Arley 

 mine " of Lancashire. Layers of nodular carbonate of iron are fre- 

 quent and have been largely worked. Some of the Coal-measure 

 sandstones near Pontefract, Ackworth, and Rotherham in Yorkshire 

 are stained red and were formerly mistaken for beds of Permian age. 



In Leicestershire these measures are about 1500 feet thick with 

 ten good coal-seams, but in Warwickshire they have shrunk to 

 about 700 feet with only five workable coals. 



In North Staffordshire they are probably about 1600 feet if 

 the group is restricted within approximately the same horizons, 

 and in South Staffordshire they are about 1000 feet thick at the 

 northern end of the coalfield, lessening to 500 feet at the 

 southern end, but this may not be entirely due to thinning. They 

 contain many good coal-seains, and it is a curious fact that some 

 fourteen seams which are distinct in the north coalesce southward 

 by the thinning out of the intervening measures till they form one 

 bed of coal, from 25 to 30 feet thick, which is then known as the 

 " Thick Coal." In Staffordshire three species of Anthracomya are 

 common in these beds A. Wardi, A. pulchra, and Adamsi. 



Transition and Upper Coal-measures. These stage* 

 have been most completely studied in North Staffordshire and 

 Flint, where Dr. W. Gibson found reason to include certain red 

 and purple sandstones which had previously been referred to tin- 

 Permian. For these he proposed the name " Keele Series," but 

 they should be known as the Keele Beds since they are only part 

 of a " series." The following is an abstract of the succession 

 established by Mr. Gibson : - 



Upper C.M. 

 Keele Beds. 



Transition 



Coal- 

 measures. 



Red and purple sandstones and marls with three thin 

 layers of Syirorbis limestone. Fossils, a few 

 plants and Entomostraca ..... 700 

 'Newcastle Group. Grey sandstones and shales with 

 four thin seams of coal and a limestone at the base. 

 Fossils, many ferns and plants (Sigillaria Urardi). 300 



Etruria marls. Red and purple marls and clays 

 with thin bands of green grit and a limestone 

 IP ir the base. The clays are largely used for 

 pottery 800 



Blackband Group. Grey sandstones and marls 

 with blackband ironstones and thin seams of coal. 

 Anthracomya Phillipsi and fish teetli . . 300 to 450 



Total about 2200 



