Horton Clay Pit is a 0.4-hectare (0.99-acre) geological Site of Special Scientific Interest in Small Dole in West Sussex.

[4] This site displays a thick and stratigraphically important sequence of rocks dating to the Folkestone Beds of the Early Cretaceous.

Researchers have used these fossils to suggest a detailed picture of the local environment during the Weichselian glaciation period and have concluded that a sour pool existed here in open heathland with a few coniferous trees.

This has been agreed in principle by Natural England if the Gault Clay is protected by a marker layer.

Additional grassland and woodland planting have been promised that will enable habitat linkages across the restored landfill.