The simple basin structure is complicated by localised folding. A smaller outcrop of Palaeocene and Eocene deposits occurs in a small syncline to the south-east of Salisbury. An anticline to the north of Portsmouth results in the significant chalk ridge of Portsdown Hill within the younger sediments; the London Clay to the north contains the Forest of Bere. A similar structure further east causes chalk to outcrop between Bognor Regis and Worthing, separated from the chalk of the South Downs by a belt of Reading Beds and London Clay continuing from Havant through Chichester and south of Arundel to the coast at Lancing.