362 ON THE MOVEMENTS OP THE EARTH^S CRUST. 



periods with corresponding bottom -moraines (and oscillations?); and 

 in the Alps there have been (according to Penck, Vergletsch. d. deiitsch. 

 Alpen) at least three glacial periods. 



We have thus filled up the curve to the present time, and connected 

 the profile of the Paris basin therewith. We will now trace the oscilla- 

 tions back to the close of the Cretaceous period in order, if possible, to 

 see how many oscillations are included in the Geological period known 

 as the Tertiary. 



The Cretaceous period is separated from the Tertiary by a period of 

 denudation, during which the land was high relatively to the sea. The 

 oldest marine formation of the Tertiary period in Europe is considered 

 to be the limestone of Mons,in Belgium. This indicates the first oscilla- 

 tion ; but this submergence 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 represented in Belgium by the so-called " sys- 

 teme Heersien," which is at the bottom a purely marine formation, but 

 has remains of land-plants at the top. Then came a new oscillation, 

 and now England also was partially submerged. Here was deposited 

 the marine Thanet Sand, and upon this the Woolwich and Reading 

 Series (=Plastic Clay), the latter partly a brackish and fresh -water for- 

 mation, 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 fresh- 

 water formation with lignite (the Lignites de Soissonnais). Then fol- 

 lowed 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 Clay commences 

 with a shore formation of shingle or gravel (Oldhaven Beds), and ihe 

 upper part of the stage shows that the sea again became shallower, in 

 consequence of a new elevation of the land.* The " S3 steme 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, six oscillations. 



The Middle Eocene is rei)resented in France chiefly by the " Calcaire 

 grossier." In this stage there are five to six sub-stages, and in sev- 

 eral places breaks in the series of deposits. The Middle Eocene is, on 

 the whole, marine, but with intercalated fresh- water beds, and it probably 



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

 probably corresponds Avitb at least two arcs of the curve. 



