Tons 



OF THE PARIS DASIN. 35 



Classification of the Paris Basin Oligocene. 



1 13. Sands of the Gatinais. 

 Aquiianian. i 12. Limestone of Beauce ; W(?«/;^ri?j' of Montmorencj'. 



In. Marls of Etampes. -] 



^ 10. Sands of Ormoy. Sands and 



9. Sand^ and pebble beds of Saclas. I sandstone of 



8. Falun of Pienefitte. I Foniaine- 



7. Sands of Van; oux. | bleau. 



6. Pebbly sands of Etrechy. J 



5. Sands of Morigny. 1 Fontenay 



4. Falun of Jeurre. ] Sands. 



3. Ostrea-nYxxXs and molasse of Etrechy. 

 2. Limestone and meulieres of Brie. 



^ I. Green marls. 



The word Tongrian is derived from Tongres in Belgium ; and 

 Aquitanian from Aciuitaine, where the beds are well developed. 



1. GREEN MARLS. 

 These plastic green clays are well known in the environs of 

 Paris, they are from thirteen to sixteen feet in thickness, and 

 have been subdivided as follows : — 



2. " Veri franc " worked for tile-making, containing rather large 

 concretions formed of sulphate of strontian mi.xed with argillaceous 

 matter. 



I. Yellow thin-bedded marl characterised by the abundance of 

 Cor/)icuta semisiriata ; this is the " Cyrena-m.a.]l " of some authors. 



The beds are of fluvio-marine origin, and are fossiliferous on 

 the northern outcrop and unfossiliferous to the south. The 

 fossils mostly consist of casts, but at one place — Fleurines, 

 between Pont-St.-Maxence and Senlis — are fairly well preserved. 

 Only eleven species of moUusca, however, are known from this 

 horizon in the whole basin.* They are — Psanunobia plana, 

 Donax Brongniarti, Meretrix incrassata, Corhiciila seniistriaia, 

 Modiolaria Branni, Bithinia Duchastcli, Planorln's defressus, 

 Potaniides plicatus, and var., P. IVeinkauffi, Natica Nysti and 

 Bayania Nysti. 



The Green Marls may be seen, amongst other places, at 



Frepillon,"!" La Ferte-Alais, Bouray, Chamarande, Etrechy, 



Corbeil and Essonnes. MM. Carez and Vasseur givej a section, 



of which the following is a resume, at the last-mentioned place : — 



Section at Essonnes. 



Wliite sandy argillaceous marls 



Green clay marls 



Whitish marls . 



Green clayey marls 



\Vhitish limestone 



Green clayey marls 



Whitish limestone 



Greenish thin-bedded marls with Cyreiia convexa 



{^Corbicula icmislriata) .... 2 2 



* Cossmann and Lambert, oj>. cit., p. 6, where nine species only are mentioned, 

 t Dollfus and Vasseur, Bull. Sac. Geol. Fr., yt. s^r., t. vi. (1878), pp. 265-6. 

 + Carez and Vasseur, Bull. Soc. Geol. Fr., 36. str., t. v. (1877). 



