458 STRATIGEAPHICAL GEOLOGY 



muddy, and in consequence a new fauna was able to establish itself 

 in French and British Seas. 



The cause of this change, so far as the British area is concerned, 

 has been discussed in my Building of the British Isles, the conclusion 

 arrived at being that there was first a slight uplift of the whole 

 area, whereby river- erosion was checked, and that this was followed 

 by unequal movements, some parts of the region being further raised 

 and others depressed. These inferences appear to be applicable also 

 to Northern France (Normandy and the Boulonnais), but not so 

 much to the central or southern parts of that country. 



Both the Bajocian and the Bathonian are well developed round 

 nearly the whole circumference of the Central Plateau. On the 

 northern border they consist entirely of limestones, the Bajocian 

 being from 150 to 250 feet thick, and the Bathonian from 300 to 

 400. In the Cote" d'Or and along the eastern side of the Plateau 

 the composition and thickness are similar, while on the south,. 

 in the Gausses district (Tarn and Aveyron), they are represented 

 by massive limestones which have an aggregate thickness of 1200 

 feet. It is only on the south-west that the marine limestones are 

 thin and are interstratified with estuarine deposits. 



No overlap of the Lias by Bajocian or Bathonian has been 

 recorded, so far as I can ascertain, though it must have taken place,, 

 and we may safely conclude that after some slight disturbances 

 subsidence proceeded in this part of France, and that the central 

 island was greatly reduced in size. The greatest subsidence was 

 clearly over the Mediterranean and Alpine region, and a broad 

 communication was opened up, through Provence, Dauphiny, and 

 the Jura, between the northern seas and a warm southern sea, by 

 means of which numerous Corals, Brachiopoda, Gastropoda, and 

 Cephalopoda made their way into the Franco- British areas. 



The Belgian island still continued to exist, though the overlap 

 of the Bathonian in Kent and the Boulonnais shows that its area 

 was diminished to some extent. There is evidence of another 

 island having existed in Servia near Milanovitz, and there may 

 also have been others within the European region. 



The whole of Northern Russia and the whole of Scandinavia 

 appear to have been land, into the western border of which small 

 gulfs penetrated from the Central European Sea. 



Clavinian Time. With respect to the early part of this epoch 

 there can be no doubt that it witnessed a still more rapid subsidence 

 of the whole European region, a subsidence which submerged 

 islands and carried the sea eastward across Central Russia into 

 Asia. This change is only partially expressed in De Lapparent's 

 maps, for though he indicates the extension of the Callovian Sea 



