THK CARBONIFEROUS SVSTKM 303 



Middle Coal-measures. These were formerly referred to 

 tlu- Upper stage because they consist chiefly of red sandstones and 

 shales, and because in some districts they appear to be unconforuiable 

 to the Lower Measures. From a study of the plant remains, 

 however, Dr. Kidston considers them to belong to the Middle 



,IV.-. 



The group has a maximum thickness of 900 feet in Fife, where 

 it comprises red sandstones, red and purple clays, with some thin 

 seams of coal and ironstone. 



In Ayrshire the unconformity at the base of these measures is 

 very marked, for they steal across the outcrops of the Lower Coal- 

 measures until they rest on the uppermost limestone of the Lower 

 Carboniferous, the Millstone Grit being absent as above stated. In 

 the Ayr coalfield these beds include a thin band of fine white 

 limestone containing Spirorbis carbonarius. A few Coal-measure 

 plants have also been obtained from them. 



Around Sanquhar in Nithsdale, Dumfries, there is an outlying 

 tract of Coal-measures which rest directly on the Ordovician rocks 

 south of the boundary fault. It has recently been proved that 

 these include both Lower and Middle Measures, and their occurrence 

 shows that Nithsdale became a strait connecting the Ayrshire 

 and Cumberland basins across a ridge which had previously been 

 an island. 



4. Ireland 



Rocks of Upper Carboniferous age occur in several parts of 

 Ireland, but the principal coalfields are four in number, two in the 

 north and two in the south. Of these the following is a brief 

 account. 



Southern Counties. One extensive area occupies parts of 

 the counties of Clare, Limerick, Kerry, and Cork, but the coal- 

 seams in this region are few and of variable thickness, so that 

 commercially it is less important than the " Leinster coalfield," 

 which occupies parts of Tipperary, Kilkenny, and Queen's County. 

 The succession in both these areas is similar, but a greater thick- 

 ness of the Middle Coal-measures comes into the western basin. 

 The groups recognised are : 



M mister. Leinster. 



4. Middle Coal-measures with several good seams of 

 coal. Fossils are freshwater Mollusca, Crustacea, 



and Amphibia 2000 800 



3. Lower Coal-measures with thin coals and shale 



roofs containing marine shells .... 900 600 



2. Flagstone group, micaceous flagstones and shales . 500 300 



3400 1700 



