584 STRATIGRAPHICAL GEOLOGY 



siliceous earths (tripoli), composed largely of Diatoms and Radiolaria, 

 witli a fauna containing some Helvetian survivals, such as Cardita 

 Jouanneti and Pecten aduncus, mixed with the characteristic 

 Sarmatian species of Tapes and Ervilia. 



7. Belgium and Germany 



Our survey of the European Miocene would not be complete 

 without a brief notice of the Belgian and German equivalents. 

 These are of small thickness, and comprise only two stages, the 

 Bolderian, which probably represents the Helvetian, and the 

 Anversian, which corresponds with the Tortonian or Sarmatian. 



The Bolderian, or sands of the Bolderberg, about 30 feet thick, 

 and contain a fairly large fauna, including Conus Dujardini, 

 Murex Nysti, Ancilla obsoleta, Terebra Basteroti, Panopcea Menardi, 

 and Venus multilamella. They rest on the Rupelian Clay, and 

 have at their base a pebble -bed containing blocks of septaria 

 derived from that clay and often pierced with P/ioZas-borings. 



The sands of Anvers (Anversian) are dark glauconitic sands 

 about 20 feet thick, and contain layers almost entirely composed of 

 the shells of Pectunculus pilosus ; other common species are Pirula 

 condita, Turritella subangulata, and Corbula striata. 



A gulf of the Bolderian Sea seems to have extended into the 

 north-west of Germany through Schleswig-Holstein, Mecklenburg, 

 and Hanover, as far as the Teutoburg and Oldenburg. The 

 deposits consist of sand at the base overlain by micaceous clay, 

 and the commoner fossils are Terebratula grandis, Area diluvii, 

 Pectunculus pilosus, Isocardia cor, Pecten Janus, P, decussatus, 

 Conus Dujardini, and G. antediluvianus. 



E. HISTORY OF THE MIOCENE PERIOD 



During the course of this period a succession of uplifts and 

 terrestrial disturbances took place by which great changes were 

 produced in the geography of Europe. The first change, i.e. that 

 from Oligocene to Miocene conditions, seems to have been a general 

 uplift, causing a general retreat of the seas, both northern and 

 southern, and raising the greater part of Northern Europe into dry 

 land. At the same time it is clear that the elevation of this land 

 was not great, and that its lower levels in France, Switzerland, 

 and Germany were occupied by large lakes. The deposit formed 

 in these lakes preserves the remains of a flora which indicates 

 a mild semi-tropical climate, inducing a rich vegetation which 

 supported a large mammalian fauna. 



These conditions seem to have continued through Burdigalian 

 time, at any rate in Northern Europe, but in the southern region, 



