LONDON DISTRICT. 



additional facts. Another object is to summarize as far as 

 possible our knowledge with respect to the method of origin of 

 the strata, and to indicate the causes which have brought about 

 the present features of hill and valley. Here it is true we have 

 to deal with some controverted questions, but the problems 

 connected with the origin and life-history of the strata and 

 with the scenery of the Thames Valley are well calculated to 

 arouse keen interest and stimulate research. 



No account of the geology of London would, however, be 

 complete without reference to other formations which lie 

 beneath the foundation of Chalk, and have been proved by means 

 of deep wells and borings. 



Following the plan of the historian it is well to begin 

 with the oldest records, and in this case with what is known of 

 the underground as apart from the surface geology. 



The following is a list of the Geological Formations known 

 to occur in the London district : 



LIST OF GEOLOGICAL FORMATIONS EXPOSED IN THE AREA 

 AND PROVED BY BORING. 



Quaternary 



Recent or 

 Holocene 



Pleistocene - 



Drift. 



Alluvium 



Thickness 

 in feet 

 up to 

 - 70 



Tertiary or 

 Kainozoic. 



Pliocene ? 



Eocene - < 



r Cretaceous- 

 Secondary J 

 or Mesozoic [^ Jumssic 



Palaeozoic - Devonian. 



'Valley Brickearth - - 30 



Valley Gravel - 50 



Boulder Clay - 35 

 Newer Plateau Gravel 



(Glacial) - - 20 

 Plateau Brickearth and 



Clay-with-flints - 30 



Solid. 



Older Plateau Gravel - - 15 



'Barton Beds 1 - 50 



Bracklesham Beds - 100 



Bagshot Beds - 120 



Claygate Beds 1 - - 110 



London Clay - 450 



Blackheath Pebble Beds - 60 

 Woolwich and Reading Beds - 80 



Thanet Sand - 80 



Chalk - 700 



Upper Greensand - - 40 



Gault - 240 



Lower Greensand - ? 



Great Oolite - - - - 87 



1 Not shown on the map. 



