594 



FAUNAL SUCCESSION OF THE UPPER BERNICIAN 



The thickness of the Carboniferous Limestone series in 

 Northumberland is difficult to estimate on account of ex- 

 cessive faulting and also owing to the great variations in 

 thickness displayed by different members. It is probable that 

 one division increases locally at the expense of another. The 

 following figures given by members of H.M. Survey and 

 others afford some idea regarding the thicknesses and 

 variations of the groups ; but they are only approximate. 



Bernician. 



Tyne & 

 Rede. 



Coquet. 



Tweed. 



Calcareous Division 



4000? 



? 



1700 



Carbonaceous Division ... 



2500 



Thin. 



900 



Tuedian. 









Fell Sandstone Series 



600 



2000 



600 



Cementstone Group 



600 



1000 



2500 



Between the Coquet and the Tweed the Cementstone group 

 thins out locally to a few hundred feet (300 or 400 ?). 



The Bernician series is mainly built up of shales and sand- 

 stones, but interbedded among the argillaceous and arenaceous 

 deposits are beds of limestone and coal. Calcareous horizons 

 are found in both divisions of the series, but the beds in the 

 upper contrast strongly with those of the lower. In the 

 Calcareous Division the limestones are thick, truly marine, and 

 constant, some of them traversing the whole length of the 

 county. In the Carbonaceous they are thin and impure, 

 and often contain rootlets of Stigmaria ; a few marine 

 limestones make their appearance in the south. It is 

 with the upper limestones that this paper is solely concerned, 

 and my investigations were restricted to the country north 

 of the Tyne. 



South of Northumberland the Upper Bernician is mainly 

 represented by the Yoredale rocks ; the basal limestones, 

 together with the Carbonaceous Division, are equivalent to 



