552 STRATIGRAPHICAL GEOLOGY 



resembling gaize or malmstone and containing diatoms and sponge 

 spicules. Farther south in the Aisne are the sands of La Fere 

 and of Chalons-sur-Vesle, which seem to be of the same age, while 

 westward near Beauvais are the sands of Bracheux, containing 

 Cyprina planata, Ostrea bellovacina, Pectunculus terebratularis, etc., 

 a fauna which is classed as Thanetian by the majority of French 

 geologists, but as Sparnacian by Professor Prestwich. 15 None of 

 these sands extend so far as Paris. 



Sparnacian. This group corresponds very closely to our 

 Woolwich and Reading Beds. Near Paris it consists principally of 

 plastic clays, but at the base is a conglomerate with bones of 

 mammals and birds, overlain by laminated clay containing Physa, 

 Viviparus, and Unio, and near the top is a bed of sand with seams 

 of lignite. This sand and lignite thickens eastward, while the 

 plastic clays die out, till in the Soissonnais the group is represented 

 by beds of lignite and black clays with associated marls and sands 

 (30 to 50 feet). These contain Cyrena cuneiformis, Melania 

 inquinata, and other Woolwich species. The highest beds are 

 found at Sinceny on the Oise. They contain the same freshwater 

 shells and consist of sands and clays with rolled flint pebbles. 



Ypresian. In France the London Clay is only found near 

 Calais and Orchies ; evidently it thinned out southward and does 

 not appear to be represented elsewhere unless by the lower part of 

 the sands of the Soissonnais, which are not more than 160 feet 

 thick. These are divisible into three portions : 



Sables de Cuise with Cyrena Gravesi and freshwater shells. 



Sables de Pierrefonds, Turritella edita and Nummulites planulatus. 



Sables d'Aizy with Rostellaria Geoffroyi. 



Lutetian. In the Paris basin this stage consists of the beds 

 generally known as the Calcaire Grossier. It is the most fossili- 

 ferous formation in the Paris basin, and the middle portion yields 

 the light-yellow calcareous freestone which is the chief building 

 stone of Paris. The group is divisible into three sub-stages as 

 follows : 



Feet. 



3. Upper, thin-bedded fissile limestones with white and green 

 marls and some beds of siliceous and dolomitic limestone, 

 Cardium obliquum, Cerithium denticulatum, Potamides 

 lapidum, Lucina saxorum . . . . . . 30 to 79 



2. Soft thick-bedded limestones, some beds largely composed 

 of Miliola and Orbitolites : Cardium granulosum, Chama 

 calcarata, Fusus bulbiformis, Turritella imbricataria . 25 to 40 

 1. Glauconitic limestones and sands with a layer of pebbles at 

 the base, Cerithium giganteum, Cardium porulosum, Ostrea 

 flabellula, Nummulites Icevigatus . . . . . 25 to 70 



80 to 145 



