504 A. Blytt on theprohabh Cause of 



tively to the sea. The oldest marine formation of the Tertiary 

 period in Europe is considered to be the hmestone of Mons, in 

 Belgium. This indicates the first oscillation ; but this sub- 

 mergence appears not to have left traces in the other Tertiary 

 basins. The first marine inundation of the Paris-basin during 

 Tertiary times formed the conglomerate of -Rilly and Nemours. 

 It was followed by an elevation of the land, and the marine 

 conglomerate was covered by the freshwater limestone of 

 Rilly. This oscillation in the Paris-basin is perhaps repre- 

 sented in Belgium by the so-called " systeme Heersien," 

 which is at the bottom a purely marine formationj but has 

 remains of land-plants at the top. Then came a new oscilla- 

 tion, and now England also was partially submerged. Here 

 was deposited the marine Thanet Sand, and upon this the 

 AVoolwich and Reading Series ( = Plastic Clay), the latter 

 partly a brackish and freshwater formation, and which shows 

 that the shore-line had again retreated. In Belgium the 

 " systeme Landenien '■* was formed during this oscillation — 

 below purely marine, above brackish. In the Paris-basin 

 there was formed the marine sand of Bracheux, which was 

 followed by a freshwater formation with lignite (the Lignites 

 de Soissonnais). Then followed a new depression, and again 

 an upheaval. This has left no traces in the Paris-basin ; but 

 in England the London Clay was formed, and in Belgium the 

 " systeme Ypresien." The London (Hay commences with a 

 shore-formation of shingle or gravel (Oldhaven Beds), and 

 the upper part of the stage shows that the sea again became 

 shallower, in consequence of a new elevation of the land"^. 

 The " systeme Ypresien" in Belgium is divided into two sub- 

 stages : — the older, a clay with Foraminifera ; the younger 

 sandy, with numerous fossils, and therefore probably indicating 

 a shallower sea. A new submergence formed, in Belgium, 

 the marine " systeme Paniselien " (sand), and in the Paris- 

 basin the marine sand of Cuise. With this the Lower Eocene 

 closes. It has therefore, in all probability, 6 oscillations. 



The Middle Eocene is represented in France chiefly by the 

 *' Calcaire grossier.''' In this stage there are 5-6 substages, 

 and in several places breaks in the series of deposits. The 

 Middle Eocene is on the whole marine, but with intercalated 

 freshwater beds, and it probably also represents 6 oscillations. 

 In Transylvania it commences (according to Koch in FoUltani 

 Kozlony, lb83, pp. 118 et seqq.) with alternations of clay and 

 marl, upon which follow alternations of gypsum and marl 

 (" lower gypsum horizon,'''' 1st oscillation). Above it, marine 



* This stage, as was shown above, contains at least 11 alternations, and 

 therefore probably corresponds with at least two arcs of the curve. 



