40 



GEOLOGICAL HISTORY. 



[CH. 



ID 

 O 



ei 

 o 

 O 



Upper Coal-Measures. 

 Transition Series. 

 Middle Coal- Measures. 

 \ Lower Coal-Measures. 



Coal- Measures! i Tranf ion Series. 



Middle Coal-Measures. 



Millstone Grit. 



Upper limestone shales and 

 Yoredale rocks. 

 Carboniferous limestone series \ Carboniferous or Mountain 



limestone. 

 \ Lower limestone shales. 

 Basement conglomerate. 



In the classification of Carboniferous rocks adopted in 

 Geikie's text-book of Geology the following arrangement is 

 followed for the Carboniferous limestone series^ : — 



Yoredale group of shales and grits passing 

 down into dark shales and limestones. 



Thick {Scaur or Mam) limestone in the 

 south and centre of England and Ire- 

 land, passing northwards into sand- 

 stones, shales and coals with limestones. 



Lower liinestone shale of the south and 

 centre of England. The Calciferous 

 sandstone group of Scotland (marine, 

 estuarine, and terrestrial organisms) 

 probably represents the Scaur limestone 

 and lower limestone shale, and graduates 

 downwards insensibly into the Upper 

 Old Red Sandstone. 



Carboniferous limestone series \ 



The thick beds of mountain limestone, with their charac- 

 teristic marine fossil shells and corals play an important part 

 in English scenery. In Derbyshire, West Yorkshire, and other 

 places, the limestone crags and hills are made up of the raised 

 floor of a comparatively deep Carboniferous sea, which covered 

 a considerable portion of the British Isles at the beginning 

 of this epoch. 



The accumulation of the calcareous skeletons of marine 



animals, with masses of coral, veritable shell-banks of extinct 



oyster-like lamellibranchs, built up during the lapse of a long 



period of time, formed widespread deposits of calcareous 



1 Kidston (94). 2 Geikie (93), p. 825. 



