278 STKATIGRAPHICAL GEOLOGY 



or bulged upward by the rising mass of lava till several submarine 

 vents were established, and during such a movement little deposi- 

 tion would take place. The probability of this view is increased 

 by a comparison of the Cornish sequence with that of Brittany, 

 where a thick volcanic series is overlain by shales that are probably 

 of Visean and possibly of Yoredale age. 



C. CONTINENTAL REPRESENTATIVES 



1. France and Belgium 



Two very different facies of the Avonian Series are found in the 

 north of France ; quite as different as those of Gloucestershire and 

 Devonshire in England, the one being essentially calcareous and 

 the other argillaceous. The former is only found in the north-east 

 of France and in Belgium, the latter occurring in Brittany, Sarthe, 

 and the Loire valley, and round the borders of the Central Plateau. 

 It will be desirable to take the former first since the succession is 

 complete and comparable with that of the Bristol area. 



Belgium, and N.E. France. The Carboniferous rocks of this 

 district lie in a set of deep and narrow troughs which succeed one 

 another along a line extending from the Boulonnais on the west by 

 Bethune, Tournai, Mons, Namur, and Liege. French and Belgian 

 geologists use the term Dinantian for this part of the Carboniferous 

 System, but as defined by them its limits are not quite coextensive 

 with the Avonian either at the bottom or the top. They also 

 divide it into two stages, the Tournaisian and the Visean, names 

 taken from the towns of Tournai and Vise. The most complete 

 section of the series is that exposed in the valley of the Meuse by 

 Hastiere, Waulsort, Dinant, and Yvoir, and the succession is repeated 

 in the basin of Namur to the north, at the junction of the Meuse 

 and the Sambre. Vise lies much farther down the valley of the 

 Meuse to the north-east of Liege, and the whole of the Vise limestone 

 has been founa to belong to the highest Avonian zone, that of 

 Dibunophyllum, and to be similar in character to that of Derbyshire ; 

 moreover, it is said to rest unconformably on the Devonian, so that 

 it is not a complete development of the so-called Visean stage. 



The most recent descriptions of the Belgian Series are those by 

 Professor de Dordolot, Dr. G. Dele'pine, and Dr. Vaughan. The 

 following is a brief summary of the faunal sequence as determined 

 by Dr. Vaughan and Dr. Delepine in a joint visit to the Belgian 

 area. 21 The normal succession is : 



