250 GEOLOGY. 



ish water, and partly by beds of fresh-water origin. They lie uncon- 

 formably on older formations. They include sands, marls, arkoses, and 

 limestones, some of which are of fresh-water origin (snail-shells, caddis 

 worms, chara, etc.). Coal is also present, and the conifers and cypresses 

 which entered largely into its composition, together with the leaves of 

 the oak, laurel, cypress, fig, maple, birch, etc., which occur in the asso- 

 ciated clastic beds, give some notion of the aspect of the vegetation 

 and of the climate. Basaltic tuff is interbedded with the other forma- 

 tions, showing that the igneous activity of the region dates back to this 

 period. In central and eastern France, there is a bed of earth so full 

 of pisolitic grains of limonite as to be worked as iron ore. With it are 

 beds of limestone of fresh- water origin, sometimes containing so many 

 bones as to be a source of commercial phosphate of lime. These phos- 

 phate deposits sometimes (Quercy) occur in pockets and fissures in the 

 Jurassic rocks on which the Oligocene lies. The Oligocene of France 

 is divided into three principal series, the Tongrian (largely brackish) 

 below, the Stampian (chiefly marine) in the middle, and Aquitanian 

 (lacustrine) at the top. 



In Belgium, the Tongrian is represented by marine beds below and 

 fluvio-marine above. The Middle series (Rupelian) is also partly marine 

 and partly non-marine, while the Upper is wanting. 



The Oligocene of north Germany is mainly marine, yet there are 

 local beds of coal, fresh-water limestone, and other formations of non- 

 marine origin at various points. Conditions for land deposition indeed 

 seem to have been rather common about the borders of the areas which 

 the sea covered, especially early and late in the period. Locally, coal- 

 beds have extraordinary thickness (70 meters at Lutzendorf). 



The Oligocene of southern Europe is chiefly marine, but in the upper 

 part of the series, lake and marsh deposits are not rare. In Italy it has 

 been estimated to have the extraordinary thickness of nearly 12,000 

 feet. The series is partly marine and partly terrestrial. 



In Switzerland, the Oligocene is represented by the upper part of 

 the Flysch formation, which overlies the Lower Nummulitic limestone 

 (p. 217), and by the lower part of the Molasse, which overlies th? Flysch. 

 The Flysch (5200 feet) is marine, while that part of the Molasse referred 

 to the Oligocene, is largely non-marine. 



The Oligocene is also represented in the Vienna basin. The Aqui- 

 tanian stage is represented by marine and non-marine beds of sediment 



