THE 



EOCENE AND OLIGOCENE BEDS 



OF 



THE PARIS BASIN. 



THE EOCENE BEDS. 



It is difficult to define the precise geographical limits of the 

 I'aris basin Tertiaries, for the reason that on the north and south 

 the beds insensibly pass, as small outliers, or en masse, into those 

 of adjacent Tertiary areas. On the north-east they are bounded 

 by those of French Flanders and Belgium, and on the south and 

 south-west by those of the Loire ; and any attempt to draw the 

 exact boundary lines of the basin in these latter areas must 

 be an exceedingly arbitrary one. The limits of the basin are 

 more clearly defined on the east by Cretaceous rocks, and on the 

 west by Cretaceous flanked by the Paleozoic and eruptive rocks 

 of Britanny. A glance at the accompanying map will show the 

 general position of the immense district included within this area. 



The Tertiary beds of the Paris basin everywhere repose on 

 the Chalk, except, perhaps, in the case of a few small outliers to 

 the north where Lower Cretaceous rocks come to the surface. The 

 junction between the Tertiary beds and the Chalk is often very 

 uneven, and there, also, the l)ed of green-coated flints, so charac- 

 teristic of the horizon over north-west Europe, is met with. 



Before commencing the detailed description of the beds wc may 

 state that, as the Paris basin is so large, and as certain of the beds 

 have only a local development, it is occasionally difficult to cor- 

 relate them one with the other, or to give their exact succession 

 or superposition. Some formations, however, have fortunately 

 a much greater extension, and are clearly traceable over large 

 tracts, so that the debatable ground of the more local beds 

 referred to is brought within very narrow limits vertically. 



The dispositions of the Secondary and Tertiary beds of the 

 basin, together with their inclinations with reference to each other, 

 and the directions of the different axes of such inclinations have 

 been well described by M. DoUfus.* 



* Hull. Sen'. Carte Giol. France, No. 14, t. ii. (1S90), Paris. 



