34 LONDON DISTRICT. 



LOCAL PARTICULARS OF BAGSHOT SERIES. 



Beginning our local descriptions with the Bagshot Beds in Essex, we 

 must note the following section which was exposed many years ago at 

 Langtons, South Weald Park 1 : 



Ft. 



Plateau /Pebbly gravel, chiefly flint pebbles, with a few quartz 

 Drift. 1 pebbles and some unworn flints - up to 6 



[Pebble-bed, wholly of flint pebbles, fine false-bedded 



Bagshot I sand interbedded with shingle in upper part ; closely 



Beds. | packed in lower part, where seams of ironstone and 



[_ layers of pipe clay occur about 15 



J Loam, holding up water. 



The pebble-bed was first grouped with the Bagshot Beds by 

 S. V. Wood, Jun., but he suggested at a later date that its age might 

 be Diestian. This view, however, is negatived by the intercalation of 

 sand of Bagshot character with the pebbles. The Eocene age of the 

 deposit was accepted by Prestwich, who also describes the sections round 

 Brentwood, more particularly in the railway cutting which lies just over 

 our eastern border. It is possible that some of the beds of pebbles in 

 Essex, shown on the map as Bagshot, belong to higher parts of the 

 Eocene ; more probably they are mixed relics of Tertiary beds rearranged 

 at a much later date, though earlier than the Chalky Boulder Clay (ftee 

 below). 2 In the outlier at High Beech some 10 ft. of Bagshot Sand, with 

 the usual thin seams of pipe-clay, may be seen in small pits near the 

 King's Oak Inn; the pebble-bed does not occur here, but the hill is 

 capped with gravel. 



In Highgate, occasional excavations have shown a bed of iron- 

 sandstone 18 in. thick, with scattered flint-pebbles, intercalated in the 

 Bagshot Sand. The bed was exposed at the Highgate end of Hornsey 

 Lane, west of the Roman Catholic School ; a large block of the 

 conglomerate has been placed by the Highgate Road, near the top of 

 West Hill. 



At Hampstead Heath a large amount of sand of the Bagshot Beds 

 has been excavated on both sides of the Heath Road ; the sections are 

 much obscured, but a pit some 20 ft. deep, showing the current-bedding 

 and other features, may be seen in the grounds of Kenwood Farm. 3 The 

 thickness of the Bagshot Beds at Hampstead has been estimated by 

 Mr. Whitaker at from 60 to 80 ft. ; but this must include part of the 

 Claygate Beds. In a MS. note dated 1840 Prestwich described the beds 

 as consisting of 20 to 30 ft. of fine white sands and coarser yellow sands 

 with layers of small rolled flint pebbles and occasional iron-sandstone 6 ft. 

 thick. This estimate agrees with the classification here adopted. 



At Harrow the pebbly bed, which passes into a ferruginous grit, has 

 again been observed. 



In the south-western part of our area relics of Bagshot Sand occur 

 beneath the Glacial Gravel at Wimbledon, Coombe Warren and Kingston 

 Hill. At Wimbledon the beds dip gently west and much of the sand 

 has been leached from under the gravel by springs thrown out by the 

 Claygate Beds. 4 A small gravel pit on Copse Hill exposes the under- 

 lying yellow current-bedded sands of the Bagshot Beds. The sands are 

 exposed in the Guildford road-cutting south of Esher, and they may be 



1 ' Geology of London ' (Mem. Geol. Surv.), vol. i, 1889, pp. 273, 274; also 

 Proc. Geol. Assoc., vol. xi, 1889, p. 19. 



'Monckton, H. W., and R. S. Herries, 'Bagshot Pebble Beds and Pebble 

 Gravel,' Proc. Geol. Assoc., vol. xi, 1889, pp. 13-23. 



8 See 'Hampstead Heath' by Members of the Hampstead Sci. Soc., 1913, 

 pp. 59-62 and Plate I. 



4 ' Summary of Progress for 1912 ' (Mem. Geol. Surv.), 1913, p. 34. 



