Ashdown Formation

Ashdown Formation
Stratigraphic range: Late Berriasian to Valanginian PreꞒ Ꞓ O S D C P T J K Pg N ↓
An exposure of the Ashdown Formation on the East Sussex coast.
Type	Geological formation
Unit of	Wealden Group
Sub-units	Fairlight Clays
Underlies	Wadhurst Clay Formation
Overlies	Durlston Formation
Thickness	typically in the range 200-230 m
Lithology
Primary	Siltstone, Sandstone
Other	Mudstone, Clay
Location
Country	UK
Extent	Weald Basin
Type section
Named for	Ashdown Forest

The Ashdown Formation is a geological unit, which forms part of the Wealden Group and the lowermost and oldest part of the now unofficial Hastings Beds. These geological units make up the core of the Weald in the English counties of East Sussex and Kent.

The other component formations of the Hastings Beds are the overlying Wadhurst Clay Formation and the Tunbridge Wells Sand Formation. The Hastings Beds in turn forms part of the Wealden Supergroup which underlies much of South East England. The sediments of the Weald of East Sussex, including the Ashdown Formation, were deposited during the Early Cretaceous Period, which lasted for approximately 40 million years from 140 to 100 million years ago. The Ashdown Formation is of Late Berriasian to Early Valanginian to age.^[1] The formation takes its name from the Ashdown Forest in the High Weald of Sussex.