CHAPTEE VI. 



CARBONIFEROUS PERIOD. 



1. Stratigraphical Evidence. 



^ABBOSTIFEROUS rocks occupy large areas in the 

 \_/ British Isles and they are known to have a wide sub- 

 terranean extension (see " Historical Geology," p. 181). 

 They exhibit three principal facies, which may be called 

 (1) the southern or Culm -measure type, (2) the central or 

 Pennine type, (3) the northern or Scottish type. 



The southern type is found in Devonshire and in the 

 south-west of Ireland ; it consists mainly of black and grey 

 shales (cleaved into slates in Ireland), the limestones being 

 very thin and insignificant. The lower part consists of 

 green and grey shales with bands of sandstone (Baggy and 

 Pilton Beds), the middle of black shales and thin lime- 

 stones (Lower Culm-measures), the upper of hard grey 

 grits with bands of shale (Middle and Upper Culm- 

 measures). 



The central type is more varied and consists of a series 

 which is divisible into four groups as follow : 



4. The Coal-measures (shales, sandstones, and coals). 



3. The Millstone Grit (sandstones and shales). 



2. The Upper or Toredale Limestones and shales. 



1. The Lower Limestones, with shale and sandstone at 

 the base. 



Nos. 1 and 2 are known as the Lower Carboniferous 

 series, and sometimes attain a thickness of 8,000 feet. 



