294 STKATIGRAPHICAL GEOLOGY 



is generally found in synclinal troughs or basins, the highest 

 portion of the series usually lying in the central parts of such 

 basins. All areas where workable coals exist are called coalfields. 



Of such coalfields there are no fewer than eighteen in England 

 and Wales, some large and some very small, and if the unpro- 

 ductive Devonshire basin is included there are nineteen. In 

 Scotland there are three coalfields in which Westphalian measures 

 are worked, besides three others in the underlying Avonian Series. 

 In Ireland there are five such basins. 



In describing the Coal-measures found in these numerous basins 

 it will be convenient to group them into natural areas wherein a 

 similar succession of strata is found, and as their most complete 

 development is exhibited in the basins which lie on each side of 

 the Pennine Anticline (see Fig. 86), these will be placed first. The 

 areas may therefore be taken in the following order : 



1. The South Pennine and Midland area. 



2. The Newcastle Coalfield. 



3. Scotland. 



4. Ireland. 



5. Bristol, Somerset, and South Wales Coalfields. 



6. Devonshire. 



1. The South Pennine and Midland Area 



This area will include the Nottingham and Yorkshire coalfield . 

 on the east and those of Lancashire and North Staffordshire on the 

 west, the latter probably being connected under the Cheshire basin 

 with the Flint and Denbigh coalfield (see Fig. 98, and the map, 

 Fig. 87). We shall also include the other Midland coalfields to the 

 southward, those of Shropshire, South Stafford, Leicestershire, and 

 Warwickshire, since they are all portions of a series of deposits 

 which originally formed one continuous sheet. 



In the basins which flank each side of the Pennine range the 

 complete succession is as follows : 



Feet. 



p.^/Red and purple sandstones and marls 

 Upper UM.j w ith thin limestones .... about 700 

 m -4.- n TVT (Grey sandstones and shales, red and 

 IransitionUM.j piu .pl e marls ; some thin coal-seams . ,, 1500 

 nvfjji n TV/T fGrey shales and sandstones with many 



iUM '\ seams of coal and ironstone . . . ,, 2500 



n TIT (Grey flagstones and black shales with 

 Lower UJVJ. j gQme coal . seams (generally thin) . . 1000 to 2500 



~ ., /'Sandstones and shales, thickening toward 

 Millstone Gnt| the north . eas t 400 to 3500 



9500 



