440 EOCENE. 



Lower Bagshot Beds. 



This deposit consists of pale yellow or buff false-bedded sand 

 and loam, with layers of pipe-clay, and occasional beds of flint- 

 pebbles. Ironstone veins and nodules are sometimes met with. 

 The thickness varies from loo feet or less to 150 feet. 



In the London Basin the beds locally show no marked inclina- 

 tion ; in the Isle of Wight they are highly inclined. (See Fig. 

 73, p. 429.) 



Organic remains of animals are exceedingly rare, only a few 

 casts of Mollusca having been found. The Leaf-beds (pipe-clay) 

 of Alum Bay and Bournemouth have yielded many land-plants of 

 subtropical genera, such as palms, maples, etc. 



Prof. Prestwich considers that the Bagshot Beds were derived by 

 denudation from the older crystalline and granitic rocks, but Mr. 

 G. JMaw has suggested that some of the fine white clays may have 

 been due to the destruction of the Chalk.' 



In sections near Brentwood the London Clay is seen to pass 

 upwards into the Lower Bagshot Beds : there the passage-beds 

 consist of alternations of clays, sands, and loams, furnishing 

 excellent brickearths. The pebble-beds in the Lower Bagshot 

 series, which are ^composed almost entirely of flint pebbles, were 

 first noticed by INIr. S. V. Wood, jun., although he has suggested that 

 they may be Pliocene.^ They occur at Brentwood, Stock, Billericay, 

 and other localities in Essex. Their thickness is 15 feet at Brent- 

 wood, where the following divisions are exposed 'J — 



Feet. 

 J ^ j 8. Pebble-beds 15 



T> 1 ^ r> J I 7- Brickearth or loam ) 



Bagshot Beds, j ^_ ^^^^^ } 25 



5. Brickearth or loam \ 



, 4- Clay ( 



London Clay. <( 3. Sand, 2 or 3 feet i -^ 



2. Brickearth or loam J 



I. Clay, with Septaria. 



From the Bagshot Beds themselves varying so much in section, and from the 

 passage upwards of the London Clay into them, it is impossible to be certain of 

 the horizon taken as the junction of the two formations in the many outliers in 

 Essex : where a purely sandy condition prevailed at one spot a loam may have 

 been formed at another, and a clay at a third. Hence around Rayleigh a larger 

 area of Bagshot Beds has been shown on the Geological Survey Maps than near 

 Brentwood, because the junction there has been taken at a lower level. 



Outliers of Lower Bagshot Beds occur at Langdon Hill, High 

 Beech, High gate (426 feet above sea-level), Hampstead (440 ft.),* 

 and Harrow, forming some of the highest hills near London, 

 and commanding extensive views. 



' Q. J. xxiii. 387 ; see also Godwin-Austen, Q. J. vi. 86. 



2 Q. J. xxiv. 465 ; xxxvi. 473. 



. 3 See Whitaker and H. B. W., Mem. Geol. Surv. iv. 320, 321, 32S. 



* C. Evans, P. Geol. Assoc, iii. 21. 



