OF THE PARIS BASIN. 4 1 



7. SANDS OF VAUROUX. 



The beds immediately above the pebbly sands of Etrechy are 

 difficult to work out. M. Lambert has demonstrated* the exist- 

 ence of three distinct horizons, the first constituting the sands 

 with CorlmloJiiya, properly so-called, containing the falun of 

 Pierrefitte, and having the sands of Vauroux at the base ; the 

 second comprises a series of lilac sands with pebbles ; and the 

 third is sandstone, or fine sand, with the fauna of Ormoy. Subse- 

 quently the same author f sub-divided the Corbulomya beds into 

 three parts, describing them in descending order as follows : — 

 (i) Falun of Pierrefitte, (2) sands of Vauroux, and (3) sands of 

 Etampes. Eventually he, together with M. Cossmann \ showed 

 that the last-mentioned sands are simply a lateral modification of 

 those of Vauroux. 



The typical section of the Vauroux sands, which occurs near 

 the College of Etampes, in the river valley at the foot of the wood 

 of Vauroux, is thus 'described by M. Lambert: — 



Section at Vauroux. 



Vegetable earth ...... 



Grey sand without fossils, with a greenish-grey vein 



Grey sand, yellowish, with some siliceous pebbles 



Thin bed of yellowish sand .... 



(^White quartzose sand with nodules c 



c 1 f I greenish-grey fossiliferous sand 



,r ■( White quartzose fossiliferous sand 



Vauroux ] ^ • , ' j • .^u- -, j 



i Greyish sand in thin beds . 



VWhite sand with few shells 



Characteristic fossils of the Vauroux sands are, Murex 

 pereger, Volutilithes Rathieri, Pleurotoma belgica, Lucina Thierensi, 

 Tellina Hcberti, Meretrix dubia and Corbulomya Morleti. 



It is difficult to trace these beds north of Etampes, because 

 they become unfossiliferous on leaving the typical area. 



8. FALUN OF PIERREFITTE. 



This is composed of white quartzose sands, sometimes micac20us, 

 indistinctly stratified, and frequently having a layer of siliceous 

 pebbles. Its mean thickness is about twenty-six feet The occur- 

 rence of fossils in this formation is purely local, the beds can be fol- 

 lowedover wide areas, and are practically unfossiliferous, except here 

 and there where they open out into rich shelly sands, especially 

 at the typical locality of Pierrefitte, which is about three miles due 

 west of Etampes. An exposure of a few feet at Pierrefitte has 

 yielded as many as 170 species of mollusca. On the occasion 



* Lambert, Sables marins dc Pierrefitte, Nouv. Arch, du Mus., 2e. s^r., t. iii., p. 257. 



+ Lambert, Bull. Soc. Gcol. Fr., 36. s^r., I. ix. (18S1), p. 479. 



{ Cossmann and Lambert, Mem. Soc. Gcol. Fr., 36. s^r., t. iii. (1884), p. 21. 



