158 



CARBONIFEROUS. 



Mr. G. H. Morton has remarked that one of the grandest and 

 most accessible exposures of the Lower Carboniferous series occurs 

 near Llangollen. The precipitous and lofty ridge known as 

 Creigian Eglwysegle, or more commonly as the Eglwyseg rocks, 

 near Tan-y-Castell, presents the whole of the beds in an unbroken 

 series, from the Old Red Sandstone to the Millstone Grit. No 

 particular band of shales intervenes between the Carboniferous 

 Limestone and Old Red Sandstone, but shales occur interbedded 

 with the Limestones.^ 



Fig. 22. — Section across the Eglwysegle Rocks, near Tan-y-Castell, 



Denbighshire. 



(Prof. A. H. Green.) 



A. Sandy Drift. B. Boulders of Igneoos rocks. 



Millstone Grit / 6. Soft fine-grained sandstone, with white quartz pebbles. 

 ] 5. Shales. 



' 4. Hard close-grained sandstone, with small quartz pebbles. 

 3. Flaggy and sandy limestone, with small quartz pebbles ; band of 



encrinital limestone at the top, 

 2. Thin-bedded earthy limestone. Corals and shells abundant. 

 I. Grey Limestone. 



and 

 Yoredale Rocks ? 



Carboniferous 

 Limestone. 



Among the fossils are Prodtictus comoides, P. gi'ganfcus, P. Llan- 

 goUtiisis, Athvn's Royssii, Spirifcra lincafa, S. bisu/cata, Euomphahis 

 Dionysii, Syrmgopora genicidata, etc. A Radiolarian {Calcisphivra) 

 and Saccamina Carteri have also been met with.* The Limestone 

 may be studied at the Trevor quarries, near Castell Dinas Bran, at 

 the Garth limestone quarries, and at Dolcoch, near Oswestry. 



South of Congleton in Cheshire the Carboniferous Limestone is 

 exposed at the Astbury limeworks. In Coalbrook Dale the lime- 

 stone is exposed at Lilleshall and Steeraways. In this district it 

 is much attenuated, being from 40 to 100 feet in thickness. 



The Carboniferous Limestone presents its characteristic features 

 and maintains great uniformity in Leicestershire, Derbyshire, South 

 Wales, Monmouthshire, Gloucestershire, and Somersetshire. Its 

 thickness, however, varies much. It is a great calcareous mass, 

 with few marked clay beds or other divisions. 



Much of the Carboniferous Limestone of Leicestershire is 

 dolomitic ; it has been quarried at Grace Dieu, Breedon Hill 

 (Breedon Stone), Ticknall, and other places. At Grace Dieu there 

 are traces of Upper Limestone Shales. (See Fig. 23.)^ 



In Derbyshire, the Carboniferous (or Derbyshire) Limestone is 

 well known in the numerous dales whose picturesque scenery is so 

 attractive, while the associated and contemporaneous masses of 



1 See also A. H. Green, G. Mag. 1867, p. 12 ; and Proc. Geol. Assoc, iv, 56S. 



2 G. W. Shrubsole, Proc. Chester Soc. Nat. Sc. 1S84, p. 106. 



3 Q. J. xviii. 137. 



