Commercially useful deposits of about 2m to 4m thick are present in Kent, Hertfordshire and Hampshire, overlying chalk, Thanet Beds or London Clay.
Eddington is approximately 13 metres above sea level, lying above mainly London Clay with some head Brickearth next to Plenty Brook; however to the east this changes to Tertiary deposits of the Thanet, Oldhaven and Woolwich beds.