150 Hind : Carboniferous Geology. 



of North Wales is succeeded by Semimda beds, a sub-division 

 of which is comparatively high up in the Bristol succession. 



Many of the present difficulties of British Carboniferous 

 Stratigraphy are due to the fact that portions of the British 

 Isles were dry land throughout the whole Carboniferous period. 

 The whole of the North of Scotland, the Southern Uplands, 

 the Lake District, parts of North-west and Mid Wales and 

 Shropshire, the Mourne Mountains, and parts of Co. Wicklow, 

 were not submerged even in lower Carboniferous times. 



Out to the East, over Belgium, the Carboniferous sea was 

 laying down deposits of Limestone, which can now be correlated 

 with the lowest part of the Bristol Series, but still further East, 

 in Germany, practically none of the lower Carboniferous Rocks 

 are found at all, and the Carboniferous Series there commences 

 with the Culm, containing a fauna which identifies those beds 

 with the Pendleside Series of the Midlands. 



In Russia, the lowest part of the Carboniferous Limestone 

 is characterised by a fauna {Productus giganteus) which is asso- 

 ciated in Belgium and Great Britain with the highest beds of 

 the Series. 



Not only locally, therefore, in the British Isles, but also 

 across Europe there 'is an extensive overlap of the higher 

 members of the Carboniferous Series, and it is of the utmost 

 importance to work out the causes and conditions of this over- 

 lap, this question being one of world-wide inportance. It 

 would seem, too, that the key to the riddle is in the County of 

 Yorkshire, and that the solution of the problem of the relation- 

 ship of the Yoredale Series and the Pendleside group will go 

 far to settle the whole question of European Carboniferous 

 Geology. 



The succession of Carboniferous Rocks in the Bristol area 

 has been described in detail by Dr. Vaughan.* The Avon 

 gorge shews, with one fault and one slight repetition, a complete 

 sequence of the Carboniferous Limestone series. Since that 

 publication, Dr. Vaughan, Dr. Sibly and others have shewn 

 that a similar sequence exists in the Mendips and in South 

 Wales. Dr. Vaughan was able to shew that the whole sequence 

 could be divided into broad life zones by the study of the Corals 

 and Brachiopods, and that these life zones could be traced 

 through South Wales. And there is very little doubt that these 



* O. J. Geological Soc, Vol. LXI., pp. 181-307. 



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