Atherfield Clay Formation
Stratigraphic range: Aptian PreꞒ Ꞓ O S D C P T J K Pg N
Atherfield Point
Type	Geological formation
Unit of	Lower Greensand Group
Sub-units	Chale Clay Member
Underlies	Ferruginous Sands, Hythe Formation
Overlies	Vectis Formation, Weald Clay
Thickness	55–60 m (180–197 ft) on the Isle of Wight, up to 18 m (59 ft) in the Weald
Lithology
Primary	Mudstone
Other	Sandstone, Ironstone
Location
Region	Europe
Country	UK
Extent	Southern England

The Atherfield Clay Formation is a Geological formation in Southern England. Part of the Lower Greensand Group it dates to the Aptian age of the Early Cretaceous. The deposit is of marine origin largely consisting of massive yellowish brown to pale grey mudstones.^[1] The pterosaur Vectidraco is known from the formation.^[2] As is the Sandownid turtle Sandownia.