90 PEOF. MOERIS — GEOLOGY OF THE LONDON BASIN 



ago -worked out by Sir Charles Lyell and M. Deshayes, and con- 

 stitute an important feature in the physical structure of modem 

 Europe. In the area of the London Basin we find two or three 

 of these divisions more or less regularly developed. In the 

 immediate neighbourhood of AVatford there arc only two repre- 

 sentatives of these di^-isions, the Eocene and Pleistocene, — one 

 belonging to the lower and older portion of the Tertiary series; 

 and the other to the far higher and more modern one. In the 

 lower formation the rocks follow each other in stratified order 

 and regular sequence. The other, or upper, is part of a wide- 

 spread group, the Boulder-clay and Glacial beds, without any 

 regular stratification, covering, without order, all preceding for- 

 mations. It is these latter I shall mention in referring to the 

 Glacial Period. 



The lower period, or the Eocene, supplies some of the most 

 marked features of the London Basin. It is divided into a series 

 of groups somewhat remarkable, and variable in their lithological 

 and paloeontological character. These are, in descending order: — 



o j Bembridge beds Fluvio-manne.' 



_al j Osborne and Headon series Fluvio-marine. 



„• / Upper Bagsbot Sands Marine. 



^ \ Barton beds Marine. 



^ j Bracklesbam beds Marine. 



^ \ Lower Bagsbot Sands and pebble-beds Marine. 



i London Clay. Marine and Estiiarine. 

 Oldhaven and Blackheath beds Marine and Estuarine. 

 Woolwicb and Beading beds Estuarine. 

 Tbanet Sands Marine. 



All the above divisions arc not represented in the London Basin, 

 but only those belonging to the middle and lower divisions, witli 

 the exception of the Barton clay, — the Upper Bagshot Sands lying 

 directly on the Bracklesham beds, as near Chobham. The upper, 

 or fluvio-mariue series, is fully developed in Hampshire and the 

 Isle of Wight, and is well represented in the Paris Basin. The 

 celebrated gypsum beds of Montmartre with their rich mammalian 

 fauna belong to this division. 



The so-called London Basin constitutes a somewhat triangular 

 area, which is bounded north and south by the Clialk treated of 

 in the previous lecture, and shown in the figure ('Trans.' vol. i. 

 p. 11); therefore it looks like a basin-shaped arrangement in which 

 the later materials of the Tertiary beds were deposited. That these 

 are posterior to the Chalk there is no doubt, but tliey do not really 

 assume the basin-shaped form known popiilarly as a basin. The 

 Chalk, although much eroded, was not scooped out before the 



• Tbe Ilempstead beds of tbe Isle of Wigbt overlying tlic Bcnibridge, some- 

 times classed with the Eocene (Jukes, 1872), arc considered to belong to the 

 Lower Miocene, and arc represented by tbe llupclmonde and Tongrian beds of 

 Belgium, and tbe Valcaire de la Beauce and Gres de l'ontai>icbleau in France. 



