20 



Bulletin 15 



330 



Fluvio- 

 lacustrine. 



Marine 

 (littoral). 



Marine. 



Classification adopted in 18 p6. 



OLIGOCENE OF HIGH BELGIUM. 



UPPER HORIZON. 



Plastic clays, variously colored, containing an 



Aquitanian flora. 

 Sands and gravels. Cross-bedded stratifiication. 

 Sandstone of Coudroy. 

 Conglomerate of the Ardennes. 

 Layers of white quartz pebbles. 



LOWER HORIZON. 



Fine sands with traces of annelids. Meuse 

 Valley. 



OLIGOCENE OF MIDDLE AND LOW BELGIUM. 

 Rupelian {Middle Oligocene). 



UPPER HORIZON. 



White sands, becoming argillaceous. 



Clay of Boom. Leda Deshayesiayia. 



Sands. 



Coarse sands and gravel. 



LOWER HORIZON. 



White sands. 



Clays. Ntiaila compta. 



Sands of Berg. PeBtinculus obovatiis. 



Green clays, alternating with sands. 



Flint gravel beds. 



Tongrian {Lower Oligocene^. 



UPPER HORIZON. 



Marls of Vieux-Joncs. Cerithium elegans. 

 Green clays of Henis. Cytherea iiicrassata. 

 Sands of Bautersem. Cyrena semistriata. 



LOWER HORIZON.* 



Green clays. 



Micaceous sands of Neerepen. 



Argillaceous sands. Osirea ventilabrum . 



Sands. 



Plastic clays. 



Gravel beds. 



Marine. 



Brackish. 



Marine. 



The lower Tongrien is referred by ^apparent to the Eocene. 



