A HISTORY OF ESSEX 



found at Mill Green, north of Frierning, by Messrs. H. W. Monckton 

 and R. S. Herries. 



Overlying the Bagshot Sands in some of the outliers there are pebble- 

 beds composed almost wholly of flint, and these belong to the Bagshot 

 Beds. The best section, to which attention was first drawn by S. V. 

 Wood, jun., was at Langtons in South Weald Park near Brentwood. 

 The pebble-bed was fifteen feet thick, and overlaid by about six feet of 

 rearranged pebbly gravel, largely derived from the beds below. Other 

 sections of the pebble-beds have been noted at Warley, Billericay and 

 Stock, where also there are reconstructed pebbly gravels above the 

 Bagshot Beds. 1 



While the Chalk indicates marine conditions of considerable depth 

 and at a distance from any land, the succeeding Thanet Sands were formed 

 in a shallow sea probably within the influence of the great Eocene river 

 which directly brought succeeding sediments. There is a great break 

 between the Chalk and Thanet Sand, as indicated in some areas by the 

 destruction of the Chalk and its layers of flints, and everywhere by the 

 change in the life of the periods : though locally the break is unaccom- 

 panied by any discordance in the stratification of the two series. 



During the period of the Thanet Sand there is no evidence, as Mr. 

 J. Starkie Gardner points out, that any elevated Chalk coast-line came 

 locally into contact with the waves. 2 After the deposition of the Thanet 

 Beds the region underwent some elevation and came under the influence 

 of freshwater and estuarine conditions. 



The Woolwich and Reading Beds indicate a temperate climate, 

 which however was gradually changing towards the sub-tropical condi- 

 tions which subsequently prevailed. The period was one dominated by 

 the great Eocene river, and it was followed by subsidence which, as Mr. 

 Gardner remarks, ushered in the Blackheath and London Clay deposits. 



The fossils of the London Clay indicate that the climate during its 

 formation was almost tropical, while the deposit itself must have been laid 

 down slowly and quietly in the wide estuary of the Eocene river. The 

 succeeding Bagshot Sands were deposited in shallower water, probably 

 estuarine in the Essex area, but passing westwards into freshwater beds 

 with many plant-remains of sub-tropical character. 



The various Eocene strata up to the Bagshot Beds were spread over 

 the entire area of Essex, and while as before mentioned some tracts of 

 Chalk in the south of England were suffering denudation in Eocene times, 

 yet later on in Oligocene and Miocene times the region was generally raised 

 above water for an extended period. It was then that the curvature of 

 the London Basin was produced, a disturbance accompanied by eleva- 

 tion and followed by immense destruction of the land. Surface agents in 

 the shape of rain and rivers began to erode channels and to wear away 



1 See H. B. Woodward, in Whitaker's Geology of London, vol. i. pp. 270-279 ; Prestwich, Quart. 

 Journ. Geol. Soc., vol. xlvi. p. 165 ; H. W. Monckton and R. S. Herries, Pnc. Geol. Assoc., vol. xi. pp. 

 1 8 and Ixv. ; vol. xii. p. 108 ; and Monckton, Nature, June 26, 1890. 



* Quart. Journ. Geol. Soc., vol. xxxix. p. 202. 



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