38 LONDON DISTBICT. 



brings up the Chalk to the surface at Chislehurst and Lewisham, 

 neutralises it near Hither Green and further north-west produces 

 the dome -structure at Deptford by intersecting the anticline 

 between the Crystal Palace syncline and the main syncline. 



In the east the disturbances along the Thames Valley are 

 continued through the anticline of Purfleet and West Thurrock. 

 where the Chalk has a northerly dip of about 10, while a gentle 

 southerly dip has been observed near Greenhithe. As suggested 

 by Mr. Whitaker, this may be a continuation of an anticline 

 which extends from Eltham to Crayford. 



It may be noticed that the hills of London, where outliers 

 of the higher Eocene beds are preserved, occur for the most 

 part in structural basins, as, for instance, Hampstead and High- 

 gate, the Crystal Palace and Shooters Hill. Dome-like structures 

 can be recognised in the low ground of Deptford and Hackney 

 Marshes. 



The deepest part of the London Trough is in the south-west 

 of our area, where the Upper Eocene beds are found : here, 

 again, the structure is not simple. A subsidiary anticline occurs 

 at St. George's Hill; on the south of the hill the southerly dip 

 accounts for the presence of the Barton Sands, while on the 

 north the dip in that direction brings the Bracklesham Beds of 

 Woburn Hill to an unusually low altitude ; on this account 

 Hudleston suggested 1 that the clays there were in the (Lower) 

 Bagshot, but Captain Lyons pointed out the structural explanation 

 of the anomaly. 2 



The inliers of Reading Beds at Ruislip and Pinner indicate 

 lines of anticlinal flexure, approximately parallel to the strike 

 of the strata between Rickmansworth and Watford. Mr. Whitaker 

 has figured some undulations in the Chalk and Reading Beds, 

 which were exposed south of Bushey Station, and these may 

 perhaps be continued in the area north-east of Letchmoreheath. 



In Essex, between Chigwell, Havering, and Romford indica- 

 tions of faulting in the Chalk have been brought forward by 

 Mr. W. H. Dalton 3 . and attention was called to a possible syncline 

 in the London Clay at Dagenham, where about 400 ft. of that 

 formation was recorded in a boring, 4 but we are informed by 

 Mr. Whitaker that the locality was Dagnam Park, about 4 miles 

 north-east of Romford, the name Dagenham having been 

 inserted by mistake in the printed record. 5 The error has now 

 been corrected. 6 



Dislocations on a small scale are numerous. In the Chalk 

 of northern Surrey Mr. G. W. Young notes slickensides showing 

 in some cases vertical, in others horizontal shifting. 7 Many 



Quart. Journ. Oeol. Soc., vol. xliii, 1887, pp. 446-454. 

 Ibid., vol. xlv, 1889, pp. 636, 637. 

 Essex Nat., vol. v, 1891, p. 113. 



Holmes, T. V , ibiJ., vol. vi, 1892, p. 145; vol. vii, 1893, p. 27. 

 ' Geology of London ' (Mem. Oeol. Surv.), 1889, vol. ii, p. 18. 

 'Wator Supply of Essex' (Mem. Oeol. Surv.), 1916, p. 232. 

 7 Proc. Oeol. Assoc., vol. xix, 1905, p. 189. 



